What is a chord voicing?

A chord voicing describes how the notes of a chord are ordered so the exact sound of a chord can be communicated. This is helpful when you want to make sure you're playing the exact same chord, at the same place on the fretboard, with the same fingering.

A G chord is still a G chord no matter how you play it. It's a chord with 3 notes: G, B, and D. But there are about one hundred ways to play a G chord all across the guitar fretboard, which means you could be playing a high G chord when a song or guitar part intends for you to play a low G chord.

A chord diagram is a great way to notate the exact way a chord is played and is fairly easy to read for most guitarists.

If says "try a different voicing of that chord a little higher," they mean rearrange the same notes in a different place on the fretboard.