With the capo you can easily change the key of a song without relearning the chords in another key. This is a lot of times done to put a song in a more comfortable range for the singer.
Here is an example. You have a song that has the chords G C D, but you need those chords to sound like they are in the key of Bb. Find the G in the chord shape column, then follow that row to the right until you find Bb. So you would capo the guitar at the 3rd fret, and the G C and D chord shapes will sound like a Bb, Eb, and F chord.
Keeping the same key,
but changing the chord shapes
A lot of times you need to go the other way. You will have a
song that is in the key of Bb, but you need to change it to a
comfortable guitar key (C G D A E).
Here is an example. You have the chords Bb, Eb and F and you
want to transpose them into a comfortable guitar key but have
the same chord sound as the original chords.
Find a Bb in the capo 1st fret column.
Follow the row back to the far left column to see what chord
shape you will play get a Bb sound when capoed at the 1st fret.
It is an A chord shape. That is a good option for transposing
your Bb chord.
Now check the other 2 chords in the capo 1st fret column and
see if they will produce a comfortable chord shape. The Eb chord
sound with the capo at the 1st fret is played with a D chord
shape, and an F chord sound is played with an E chord shape.
Capoing at the 1st fret is a good option for transposing these
You could then go through the same process for all of the
other capo frets to find some other possibilities. And in this
case there are 3 more frets that work. Though the possibility
on the 8th fret and 10 fret are not very common since they are
so high up on the neck.
Here is the transposition chart with all of the
possibilities for the Bb, Eb and F chords. The yellow cells show
when the desired chord sound can be produced with a basic open
position chord when the guitar is capoed at that fret. The blue
cells indicate when the chord sound can not be produced with a
basic chord shape. There are a couple of frets that you could
get 1 or 2 easy chords, but not all 3.