Q: what does the second number in a time signature mean
A: what note is a beat. for example, 4/4 means the quarter note is 1 beat. the top number (first number) tells you how many beats per bar, and the bottom (second) number tells you what kind of note gets 1 beat. 7/8 would mean there are 7 beats per bar and an 8th note gets 1 beat. actually when it's 8th notes, usually it's a cheat because usually the real beat is on a larger note, for example 7/8 would more accurately be represented as 3.5/4, because usually 7/8 is felt with the quarter note getting the beat and it feels like 3 and a half beats per bar. and in 6/8, most of the time the dotted quarter note gets the beat so in that case it would be more accurately represented as 2/1.5. Also in some places in the world such as britain, the notes are not called 8th notes and quarter notes, so in that case this explanation would be rubbish