When a guitar players uses a capo, and plays a chord, it is not really that chord that is getting played. If a bass or keyboard player wants to play the same chord you have to transpose it. This application will transpose the chords for you for the fret that the capo is placed on. This makes it simpler for everyone else and the guitar player can use their capo as much as they want.
You can also save a fret setting with a song title to come back to later.