If you use iTunes to store and organize your TV Shows then things can quickly turn into a mess if you haven't labeled or tagged them properly.
Descriptor is a small widget that lets you add additional information to your television shows on iTunes via EPGuides.com and TV.com. It automatically retrieves data so that your listings are more accurate and easier to catalog and organize. You can then organize long-running TV series by episode or date of production and release.
Specifically, Descriptor enters a description of the TV show, the title of the show and episode, the year of release, episode number, and season number. The problem is that frequently, it either can't retrieve data for the shows you want it for or the data remains incomplete. It can also mean that iTunes doesn't organize the files correctly because sometimes the data retrieved can also be inaccurate.
However, Descriptor is a far faster way of keeping things in order than going through your TV series torrents and downloads one-by-one.