How to Choose Between Digital or Acoustic Piano

Digital pianos are electronic devices that use sound chips and speakers to reproduce piano sounds. Some may have eight octaves, but they may have only six, or even as few as four. Four octaves will allow you to play simple tunes, but six or more octaves will be required if you want to study music seriously.

The tone and touch of an acoustic piano is usually far superior to a digital piano. Acoustic pianos have a large number of black and white keys, spanning up to eight octaves. Acoustic pianos create a natural reverberation in the room where they are played.
Most digital pianos have a MIDI output which allows you to connect them to a computer via an inexpensive interface, which allows you to record and edit your playing and add additional parts, as well as control other instruments.
Continuation here: http://www.wikihow.com/Choose-Between-Digital-or-Acoustic-Piano