Count like this:

ONE and TWO and THREE and FOUR and... etc...

Now count like this:

ONE and two AND three and ONE and two AND three and...

Either way, there are four beats, so why does the second way feel so different? Because of the implied polyrhythm (two against three):

a) ONE and TWO and THREE and ....

b) ONE and two AND three and ...

Try tapping a with your left hand and b with your right hand.