Tiki profiles allow you to apply a pre-defined configuration to your Tiki. You can apply them through the Profiles Wizard or Local Profiles or through the Admin Panel Profiles. In Tiki terminology, a "profile" is a set of site configuration preferences and website item creation instructions that are applied as a group. The website https://profiles.tiki.org/ is the main repository for these.
Profiles don't contain or create files. They only add or edit content in the site's database. Some profiles are simple, like a contact form, and some are more complex. When they are applied, new features are activated, pages are created, permissions are changed, a new Tracker may be created to store records, and so on.
Anything that applying the profile does at the site can be undone or modified and so on. However, these adjustments will need to be done individually. There's currently no way to undo all the actions of the profile with one click. For this reason, it's a good idea to look at the details of the profile before applying it, to see, as closely as you can, what specific changes will be made in your site. This doesn't apply to site configuration profiles, but once you have a site set up, you'll want to be sure that applying a new profile doesn't disturb any of your current settings.