Barre Chords

Barre chords are movable chord patterns that enable the chord type to
easily be played at any fret position on the fingerboard.
The barre chord technique makes it possible to quickly build a chord in any
key by moving the chord shape
to a new root note.
The barre formed by the first finger is equivalent to relocating the
nut on the fingerboard, similar to how
a capo allows open string chords to be
played in an alternate key.

A barre chord is a type of movable chord.
The same chord shape can
be played at any fret
on the guitar fretboard.
In this way, the chord type - Maj, Min, etc- can be played
from any of the 12 possible root notes
of the scale on the guitar fretboard.
Barre chords are formed by
pressing a finger, often the index (first) finger,
across two or more strings at the same fret.
The frets engaged by the first finger are played simultaneously,
usually along with other notes as in a regular chord.

A barre chord is a guitar chord
that can be played in any key. For instance,
an Em chord shape
(all strings played with 2nd frets of the
2nd & 3rd strings* engaged), is an Am chord when
the index finger is pressed across all the strings at the 5th fret,
with the 2nd & 3rd strings at the 7th fret engaged.
Keeping the fretting hand firmly in this gesture,
the barre chord shape can be repositioned to
ascend or descend to any other tonic (root note)
on the guitar fretboard scale.
Thus, this Em barre chord shape played
at the 5th fret as an Am chord, is then a Bm chord
when transplanted a whole step (2 frets) up the scale.

With the barre technique, chord shapes are played
with different fingerings.
The first finger forms the barre, holding several strings
across the fingerboard at a fret position;
so there are no open strings in the chord shape.
The barre provides a base for the 2nd, 3rd, & 4th fingers
to hold the remaining notes & form chord shapes.
The chord holds the same shape
as it is repositioned to
another fret position- Similar to a power chord.
Barre chord shapes can be moved anywhere along the fretboard to any
tonic note to play the chord in that key.