Barre

A technique for stringed instruments to effectively change the scale length of the neck by use of the finger. Typically, the first finger is laid across the neck and if necessary, the other fingers are used to press down on individual strings.

Barré (or Barre / Bar) Chords are chords of the same shape which you can use up and down the fretboard.
Each position sounds a different chord, but the shape remains the same so it's easy to master.

Often used on the Guitar and Bouzouki.