If your instrument has Barres going from top to bottom then it's an Autoharp. These vary from three to 21 chords (buttons) but are normally (to be any good) twelve, fifteen & twenty one barres (Chords) These are quite easy to learn to play simple tunes on .
If it has JUST strings then it's a ZITHER. These are played purely on the strings (like a harp) and are far more diffucult to learn to play basic tunes than is an autoharp. Autoharps are also GREAT in bands. Zithers really need to be played solo. Don't forget. THE MORE THE BUTTONS THE MORE CHORDS YOU CAN PLAY!
Hope this helps.