1 bar is every 4 count,

1 bar-- 2 bars---3 bars--4bars
1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4
---S---S---S---S---S---S----S---S


S=Snare

In any song, you can count the bars by imaging an extra snare in between the real ones.

Bar usuallygo in sets 2, 4 , 8 , 16