Deck is a multitrack recording and mixing environment. What that means is you have multiple tracks that you can use to layer and arrange audio files relative to each other. For example, if you were recording a band or ensemble, you could record each instrument on separate track. This gives you a lot of flexibility because you can adjust one portion of the recording without affecting other portions. Maybe one person in the band is playing quieter than the rest and you need to make just that instrument louder, or you want to put reverb on only one instrument. By having the audio on separate tracks, you can make edits to one section without affecting the entire recording. Another way Deck is useful is for post-production for video. For people who use iMovie or Final Cut Pro Deck can be a great way to quickly and effectively create a multitrack soundtrack for your video. You can have dialogue on one track, music on another track, and add sound effects to several other tracks. With control over each individual track you can create an overall mix of the sounds for your video production.

Some common uses for Deck are:

Recording bands in a studio environment
Audio for video and post-production
Any audio project that requires you to mix together multiple sound sources