Confused on music theory?

I'm trying to make flash cards so I can memorize my scales and BEADGCF and FCGDAEB :)
However, I am extremely confused. I'm trying to write the one with no flats or sharps. Is it Concert C Major or Concert Bb? I'm referring to my clarinet book. I am so confused on why there are two letters next to each scale.

Here's what I mean:
Bb/C (no flats/sharps)
F/G (One sharp)
C/D (Two sharps)
G/A (Three sharps ect)

Why are there two letters? And I'm only trying to learn treble clef right now, so no bass clef :)
 
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