CatDV stores clip details and their thumbnails in a catalog:
Catalogs are normally saved in a file with extension .cdv. You can open more than one catalog at the same time and copy and paste clips between them. Catalogs are portable between Macintosh and Windows.
The trial version of CatDV will not normally let you save catalogs (or export or print data).
With the optional CatDV Server, CatDV users can store clips in a central shared database rather than in files on the local file system. Even then, however, CatDV still uses the concept of catalogs as a logical grouping of related clips.
Regardless of whether you are using the single-user or the networked version of CatDV, to keep catalogs a manageable size it's a good idea to have a separate catalog for each tape, or perhaps each project, rather than storing all your clips in one huge catalog. See managing multiple catalogs for hints on how to manage a large clip library.
In a self-contained archive the catalog is combined with the preview files for that catalog in a single directory (Windows) or directory bundle (Mac OS X). The archive can be saved to an external drive or copied to CD/DVD and when the archive is opened the corresponding previews are immediately accessible. With self-contained archives it is not necessary to keep all the preview files in one place. Archives have the file extension .cdvp.
You can use the Manage Preview Movies command to check which preview files are contained in an archive.