The Collect Files command gathers copies of all of the files in a project or composition into a single location. This is useful as a step before rendering, for archiving, or for moving a project to a different computer system or user account.
When you use the Collect Files command, After Effects creates a new folder in which it saves a new copy of the project, copies of the footage files, proxy files as specified, and a report describing the files, effects, and fonts necessary to recreate the project and render the compositions.
After you collect files, you can continue making changes to a project, but be aware that those changes are stored with the original project and not with the newly collected version.
The names of these folders appear in parentheses to signal to any attending render engines that they should not search these folders for projects.