There is a reason we switched to counting to four in the last example. To keep track of our counts, notes are grouped together into bars (or measures). The first type of bar we will see will use the time signature of 4/4 (four-four), written :

This number is like a fraction. The top four tells us each bar will have four counts and the bottom four tells us each count is a quarter note (if the bottom number was a two, then each count would be a half note). 4/4 is the most common time signature you will see and it is the only time signature we will be using for a while. Other common top numbers are 2 (as in marches) or 3 (used in waltzes). The bottom number is usually four, but as noted above, other numbers can be used.