To make things kind of simple (this is a subject that is hard to make simple)
the Blues Scale is spelled out as
root, flat 3, 4th, flat 5, flat 7, octive
take the Cmaj scale
CDEFGABC the blues scale of this would read
C, Eb, F, F#, G, Bb, C
you can apply this to any major scale
the Blues Scale is spelled out as
root, flat 3, 4th, flat 5, flat 7, octive
take the Cmaj scale
CDEFGABC the blues scale of this would read
C, Eb, F, F#, G, Bb, C
you can apply this to any major scale