Explanation:
The top number of the time signature tells you how many beats to count. This could be any number. Most often the number of beats will fall between 2 and 12.
The bottom number tells you what kind of note to count. That is, whether to count the beats as quarter notes, eighth notes, or sixteenth notes. So the only numbers you will see as the bottom number (the denominator) will correspond to note values:
1 = whole note (you’ll never see this)
2 = half note
4 = quarter note
8 = eighth note
16 = sixteenth note
You could continue on with 32, 64, but you will hopefully never encounter them! After a while it gets a bit unwieldy. The most common bottom numbers are 4, 8 and 16.