Basically you can specify a chord name, set the instrument and tuning and you can get the chord diagrams for all the variations of the chord. The all come back as images so I sometimes copy and paste them if I am writing something. I play a lot of C D and G in my songs so sometimes its nice to play the same chord but with a different tone so all my songs dont always sound the same anyway
Also, Powertab and GuitarPro have some good dictionaries for chords.. And GuitarPro has a TON of scales.