... C  C#  D  D#  E  F  F#  G  G#  A  A#  B  C  C#  D  D#  E  F  F#  G  G#  A  A#  B  C ...
The sharp sign (#) raises the note one fret.

The same notes can also be written like this:
... C  Db  D  Eb  E  F  Gb  G  Ab  A  Bb  B  C  Db  D  Eb  E  F  Gb  G  Ab  A  Bb  B  C ...
The flat sign (b) lowers the note one fret.

The distance between each note is one fret. When you put a capo on the third fret, a chord, or a key, will be raised three frets. So the D position with the capo on the third fret will give you an F chord (count from D in ascending order). And an A7 position will give you a C7 chord. It's as easy as that. All you have to do is to learn the names of the twelve notes and count the frets.