Fourteen years ago, I ripped several Faith No More CDs to MP3. At the time, I used a naming scheme that made lots of sense to me--I called the files "01.mp3," "02.mp3," and so on. I felt quite clever at the time, because by adding a leading zero I could get Windows Explorer to sort the files correctly.
Today, that naming scheme doesn't really work for me. I carefully file my music collection according to artist and album, with each filename containing the complete track name preceded by its number ("05 Tremendous Dynamite.mp3"). Converting my ripped MP3s to this scheme manually would take a long time, and could be a frustrating experience.
One step above completely manual conversion would be tagging the files using the CDDB database or FreeDB.org. These are both old, established projects (the latter based on the former) that work to recognize music according to its "." However, they're both focused on complete CDs rather than individual tracks. In contrast, the MusicBrainz database (which Picard queries) is built around tracks, with each individual track getting its own fingerprint.
Another issue is that both systems employ user-generated content with no filtering. That means you can get ten listings for the same CD, or listings full of typos and strange capitalization. MusicBrainz lets users edit content, but other users must before it gets entered onto the database and served up in reply to queries. This makes for better results and less duplication.
Getting up to speed with MusicBrainz Picard can take a few moments. The first step is to "throw" your files into the app--you can literally drag and drop them in, or do it with a built-in folder tree. You then need to "Cluster" them, which divides them into sensible groups (by album, usually).