The FORMAT control block is used to create individually formatted objects that can then be used in any of the individual OUTPUT methods.

Note that in some cases the field that will be displayed has its own behavior and it can clash with the format you selected.
IE: A tracker field that is a "title" is pre-formatted as a link. If you set the format as "objectlink" (or you set the display inside a link) the display will end broken as Tiki will try to display a link inside a link.

For the default parameter, it's important to remember that the tracker field "Files" works a bit differently than the others with this parameter. The tracker field Files expect an Id from the File Gallery. When most of the other fields type will display the text of the default parameters the default for "Files" must be an existing file in a gallery. The file can be an "anonymous" portrait file or a plain white image or an image with only the text "Not Available", etc. Whatever you feel right for your usage.

In most of the examples shown in PluginList output control block and PluginList advanced output control block you will see a FORMAT control block have been used. E.g. in the example shown for Table output as below, two FORMAT control blocks are used:

{LIST()}
   {filter type="trackeritem"}
   {filter content="water"}
   {OUTPUT(template="table")}
       {column field="title_link" sort="title" label="Title"  mode="raw"}
       {column field="description" label="Description"}
       {column field="event_date" sort="tracker_field_18" label="Event Date"}
   {OUTPUT}

   {FORMAT(name="title_link")}{display name="title" format="objectlink"}{FORMAT}
   {FORMAT(name="event_date")}{display name="tracker_field_18" format="date"}{FORMAT}
{LIST}

The first FORMAT control block defines an object with the name title_link that is displayed in a specific way - this object reference is then used in the column control block in the body of the table OUTPUT. Similarly the second FORMAT control block defines the event_date object which is also used in a column control block.

A similar use of the FORMAT control block allows the normal set of Smarty variables, eg {user} etc, to be made available in Smarty templates - for example:

{FORMAT(name="theuser")} { {user} } {FORMAT}

This creates a reference object theuser with the userId of the current user which can then be invoked in a server stored smarty template using the variable {$row.theuser}.

{LIST()}
  {filter field="tracker_id" content="1"}
  {filter field="tracker_status" content="o"}
  {OUTPUT()}
        {DIV(class="h3")}{display name="name"}{DIV}
          {display name="photo"}%%%
          {display name="email"}
  {OUTPUT}
  {FORMAT(name="name")}{display name="tracker_field_userName"}{FORMAT}
  {FORMAT(name="photo")}{display name="tracker_field_userPhoto" format="trackerrender" default="1140"}{FORMAT}
  {FORMAT(name="location")}{display name="tracker_field_userLocation" format="trackerrender" default="Unknown"}{FORMAT}
{LIST}

Default parameter applied on the "photo" field will display a default generic image if not file found.
Default parameter applied on the "location" field will display the text "Unknown" if the field is empty.

You might want to display all comments, and this script will retrieve them:

{LIST(cache="n")} 
{filter type="comment"}
{pagination max="10"}
  {OUTPUT( template="table")}
    {column field="title"}
    {column field="comment_content"}
    {column field="object_link" mode="raw"}
    {column field="date"}
{OUTPUT}
  {FORMAT( name="object_link")}
    {display name="object_id" format="objectlink"}
{FORMAT}
  {sort mode="date_desc"}
{LIST}

The FORMAT control block defines an object with the name object_link which is displayed in such a way that it is object_id which is displayed and formatted as objectlink; which makes the id clickable. This object reference is then used in the column control block in the body of the OUTPUT table.
This gives us the following result:

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We see that this only gives us the information about the object (the comment in this case), but what if I want to have more information before visiting the comment?

One way to do this is to add a column which indicates the item being commented on. It is typically a wiki page or tracker item which is clickable and takes me there.

So let's make some changes and see what we have:

{LIST(cache="n")} 
{filter type="comment"}
{pagination max="10"}
  {OUTPUT( template="table")}
    {column field="contributors"}
    {column field="title"}
    {column field="comment_content"}
    {column field="parent_object_title" mode="raw"}
    {column field="object_link" mode="raw"}
    {column field="date"}
{OUTPUT}
{FORMAT( name="object_link")}
    {display name="object_id" format="objectlink"}
{FORMAT}
{FORMAT( name="parent_object_title")}
    {display name="parent_object_type"}: {display name="wikiplugin_objectlink" format="wikiplugin" type="parent_object_type" id="parent_object_id"}
{FORMAT}
  {sort mode="date_desc"}
{LIST}

Here we have just added a new column whose label is "Parent Object".
The new FORMAT control block formats the parent_object_title field, which is the title of the comment's parent object, then with {display} tag we first display the name of the parent object, which is stored in the parent_object_type field. For example, if the parent object is a trackeritem, it will display "trackeritem:", and finally we display the link to the parent object, using the wikiplugin_objectlink plugin. This plugin allows you to create a link to a Tiki object according to its type and its identifier. Here you specify the link format as "wikiplugin", the object type as parent_object_type, and the object id as parent_object_id. For example, if the parent object is a trackeritem with id 1, this will generate a link to "tiki-view_tracker_item.php?itemId=1".
So you get a field that displays the name and link of the comment's parent object. For example, if the comment is linked to an item called "This is my first item", you display "trackeritem: This is my first item".
This gives us the following result:

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Tweaking the sample above and using font awesome (integrated in Tiki) you can display corresponding icons for a content.
In this demo case we have a tracker with a "gender" field that hold 2 values, "male" or "female". There is a "male" and a "female" icon in Font Awesome and as both use the same term we can assign it to a div type icon and class.

{LIST()}
  {filter field="tracker_id" content="42"}
  {OUTPUT(template="table")}
    {column label="Title" field="title" sort="title"}
    {column label="Gender" field="gender"}
  {OUTPUT}
  {FORMAT(name="gender")}{DIV(type=i class=fa fa-{display name="tracker_field_gender"})}{DIV}{FORMAT}
{LIST}

In this wikiplugin embedded in a smarty (or wiki) template the field is set to be editable inline (note: format="trackerrender" is required ad well as the Inline editing (found in admin control panels=>trackers)

{wikiplugin _name=list}
  {literal}
    {filter content="2" field="tracker_id"}
    {output(template="mytemplate.tpl")}
    {ALTERNATE()} empty {ALTERNATE}
    {FORMAT(name="name")}{display name="tracker_field_name" editable="inline" format="trackerrender" default=""}{FORMAT}
  {/literal}
{/wikiplugin}

So the 2nd column uses a FORMAT plugin where the contents of the field in question, tracker_field_data, is used as the class for a div but the default (used if the data field is empty) is set to be the bootstrap class "hidden" so the contents, the check mark, only appears if there is some data.

Obviously if the data is the name of some other class weird stuff might happen, but for most usual cases, it works as expected and saves having to make a new smarty template just for this simple list.

(Tip and example taken from a message from JonnyB in the developers list - thanks!)

Tweaking the sample above and using font awesome (integrated in Tiki) you can display corresponding icons for a content.
In this demo case we have a tracker with a "gender" field that hold 2 values, "male" or "female". There is a "male" and a "female" icon in Font Awesome and as both use the same term we can assign it to a div type icon and class.

{LIST()}
  {filter field="tracker_id" content="42"}
  {OUTPUT(template="table")}
    {column label="Title" field="title" sort="title"}
    {column label="Gender" field="gender"}
  {OUTPUT}
  {FORMAT(name="gender")}{DIV(type=i class=fa fa-{display name="tracker_field_gender"})}{DIV}{FORMAT}
{LIST}

When you use a template to display your plugin list you want other item related or linked to the item to open using the same template (or another it doesn't matter) but not to open the trackers built-in system. For this you need to enable the Alias feature and set it to use the template to display the tracker item, "record-" for this sample.

When you use an item link to link an item to other item (related, friend of, etc.) this is a kind of a problem.
Item link has 2 option to display and item link. Value and Link.
Value display the id of the content (ie: 6).
Link display the value of the content linked to the tracker item (ie: Bernard).

Your link should be like:

[record-6|Bernard]

So it open the item "Id6" in the "record-" template showing the value "Bernard" for the link.
To achieve this you need to create and use 2 row.

{FORMAT(name="name")}{display name="tracker_field_contact" format=trackerrender}{FORMAT}
{FORMAT(name="id")}{display name="tracker_field_contact"}{FORMAT}

The first one with format=trackerrender will display the content of the tracker Item Link field as it is shown in the tracker (Bernard).
The second one without the format=trackerrender will show the real value for this field (6).

The assemble your link as follow:

[record-{display name="id"}|{display name="name"}]

It will complete the trick and open the item 6 using the record- template while the link displayed will show the right value, Bernard.

Instead of using wiki format, you can specify template or tplwiki arguments to refer to a smarty template stored in a file or a wiki page. See PluginList-output-control-block#Parameters for more info on accepted values.

All the LIST Plugin control blocks