Adjusting the action on an acoustic guitar is the process of setting the string height above the fretboard. The action is important because it affects the playability and tone of the guitar. A guitar with too high action can be difficult to play, while a guitar with too low action can cause buzzing and fretting out.
The ideal action height varies depending on the guitar and the player’s preferences. However, a good starting point is to set the action so that there is about 0.010 inches of clearance between the bottom of the strings and the top of the frets at the 12th fret. This can be measured using a feeler gauge or a ruler.