Open chord

An open chord is a chord played near the nut that uses at least one open (unfretted) string. It's where nearly every guitarist starts, before barre chords, which require fretting every string yourself.

What the open string actually changes

Beyond being easier to play, an open chord sounds different from an equivalent barre chord: the open string(s) ring longer and louder than a fretted one, giving open chords a richer, more overtone-heavy tone — one reason many guitarists still prefer them even once they've mastered barre chords, not just out of ease.

The sheet Blues in E — getting started uses only open chords (E, A, B7), to stay accessible right from level 1.