A time signature is similar to a fraction. In that the bottom number tells what the divisions are, while the top tells how many of them there are.

So, in 4/4 the bottom 4 tells each 'beat' is a crotchet (quarter note), while the top 4 tells there are 4 of them in each bar. Similarly with 3/4. 3 crotchets per bar. 5/4 tells 5 crotchets per bar, unsurprisingly.

6/8 tells there are 6 quavers in each bar, which is the same as 3/4 mathematically, but actually doesn't reveal that the rhythm of the bar is quite different, though. That's often where the confusion between 3/4 and 6/8 is found. 7/8 unsurprisingly tells 7 quavers (eighth notes) in each bar - but again, a little like 6/8, doesn't give a clue in itself how those quavers are grouped, rhythm wise.

A time signature is similar to a fraction. In that the bottom number tells what the divisions are, while the top tells how many of them there are.

So, in 4/4 the bottom 4 tells each 'beat' is a crotchet (quarter note), while the top 4 tells there are 4 of them in each bar. Similarly with 3/4. 3 crotchets per bar. 5/4 tells 5 crotchets per bar, unsurprisingly.

6/8 tells there are 6 quavers in each bar, which is the same as 3/4 mathematically, but actually doesn't reveal that the rhythm of the bar is quite different, though. That's often where the confusion between 3/4 and 6/8 is found. 7/8 unsurprisingly tells 7 quavers (eighth notes) in each bar - but again, a little like 6/8, doesn't give a clue in itself how those quavers are grouped, rhythm wise.

The concept of a 'whole note' :- a whole note is called a semibreve, which is made up of two minims,(1/2 notes) or 4 crotchets,(1/4 notes). It is the hollow egg-shaped note, with no stem. It doesn't have too much bearing on things - except that it is the 'whole' that is divided, as explained in this paragraph. A whole note will fit into one bar of 4/4, but not into a whole bar of 3/4. Hence 3/4 gets called 'three-quarter time' quite often. That, and after all, it looks exactly like the fraction - 3/4!