Guitar action refers to the height of the strings above the guitar fretboard. It affects how easy or difficult it is to play the instrument. Lower action makes it easier to press the strings down, which is beneficial for beginners or those who prefer a lighter touch. However, if the action is too low, it can cause fret buzz, where the strings vibrate against the frets, producing an undesirable sound. Adjusting guitar action involves changing the bridge or nut height, or adjusting the truss rod, which affects the neck's curvature. Proper action is essential for optimal playability and tone, allowing musicians to perform comfortably and effectively.