`What does the '°' notation signify?
diminished, which means that you play a minor chord with a flattened five.
`What does the 'X/Y' notation signify?
This is called
This means that you play an inversion of the
X chord where the lowest note is
C/G is played as
In some cases, like the ones that you present, an extra note might be added that is not necessarily a part of the original chord.
C/Bb is played as
G, which is just an inversion of
C7 with the seventh note in the bass.
I found this site to useful: https://www.pianochord.org/
To find out what
D° means, then you
D in the top bar
- check through the
D chord categories; since it's not there, you
- go down to the
Ddim - D diminished (D°)
Ddim in the listing above
This gives https://www.pianochord.org/d-dim.html
On the website, you also get help to fingering.