The term "bar chord" means that the first finger bars across either all the strings, or some of the strings. The fact that there are no open strings in a bar chord means it is possible to move the one shape to all positions of the fretboard and play in every key. The diagram and photo below demonstrate an F major bar chord. Notice that this chord is simply an E chord shape played with the 2nd, 3rd and 4th fingers, with a first finger bar behind it.