The Autoharp is a string instrument from the Zither family. The autoharp most commonly played today is based on the original instrument invented by the German born American, Karl August Gütter in the late 1800s.
It can be played; on a table, resting across your the lap while seated, or resting against the left shoulder (a strap can be very helpful if your instrument is weighty). A felt or plastic pick held in the right hand can be used to strums the strings. Appalachian players can be seen playing with finger picks (bluegrass banjo style), whilst folk players use their right hand thumb. The left hand is used to play/ depress the buttons which control the bars that dampen all the strings except those of the selected chords.
Tuning can “… diatonically (i.e., using a scale or scales based on seven steps to the octave) or chromatically (i.e., using 12 semitones to the octave), and the number of chord bars varies from as few as 3 to as many as 27, with 15- and 21-chord models being the most popular. The instrument has been used for teaching simple harmony.” (Source https://www.britannica.com/art/autoharp)