Place your pointer finger on the 5th fret of the low E string. Now place your ring finger on the 7th fret of the A string. Strum both strings.
This is a Power Chord!
You can play a power chord anywhere on the fretboard, starting at any fret! Try moving your power chord around and see what cool rhythms you can make!
The technical definition of a power chord is a root and its 5th (fifth note in scale)