If you place a capo on the second fret, you have effectively moved the nut ( The white plastic peice ) up two frets.
All your open chords will be higher.
A C shape chord will be D
An A shape chord will be B
A D shape chord will be E
An A minor shape chord will be B minor
An E minor chord will be F sharp minor
An E chord shape will be F sharp

A Capo allows you to play more different chords, if you only know a limited amount of open chord shapes