Every song has a time signature. This dictates the rhythm of the song. The vast majority of music you hear in pop music is in 4/4 time -- four beats in a measure or "bar," a quarter note (written as a dot with a stick on it in 4/4 time) represents one beat. A whole note (written as a circle) takes up an entire bar of music, an eighth note looks like a quarter note with a flag, a sixteenth note has two flags.
Below you should see what a basic beat would look like written out over two bars: the top line of notes represents notes played on the closed hi-hat, the middle line is notes played on the the snare drum, and the bottom line is notes played on the bass drum. Notice it contains sixteenth notes, eighth notes and quarter notes. The way a drummer would count with quarter notes is to play a note on the counted number -- "one, two, three, four." When eighth notes are introduced the notes are played by counting "and" -- "one, and two, and three, and four, and..." Sixteenth notes are counted by a drummer saying "ee" and "ah." -- "one ee and ah two ee and ah three ee and a four ee and ah..." Click on the diagram below to hear how this plays out:
This is a pretty simple beat that you would hear in a funk song. Something congruous to this specific beat appeared on the Stevie Wonder song "Superstition."
Time can be a tricky business. For a westerner to play 4/4 time is fairly easy, because it is a rhythm the person grows up hearing all the time. But try playing in 5/4, 6/8, or 7/8 sometime... it can be challenging if you are not used to those sorts of rhythms. Think of the theme from "Mission Impossible": this is a deceptively tricky song for an orchestra to play, because it's in 5/4 time, and the instrumentation is syncopated -- it offsets the time signature. The odd time of that tune gives it its distinctly elusive characteristics -- it sounds like a song that a secret agent would play in the car.
Below is a figure in 6/8 time. Something roughly similar to this rhythm was played by John Coltrane when he remade "My Favorite Things" from "The Sound of Music" and when he wrote the composition "Afro Blue."In this figure, the top line is the ride cymbal, played with the right hand, and the "x" in the middle is the hi-hat clicked by the left foot. The bottom note is the bass drum. This is substantially different from a rock beat, because rock n' roll drumming tends to emphasize the bass drum (right foot) and the snare (left hand), whereas jazz drumming emphasizes the hi-hat (left foot) and ride (right hand). Click on the figure to hear the rhythm on the drum set.
One last note about time signatures -- like fractions they can be reduced, 6/8 time can be counted as 3/4, this depends largely on the preferences of the musician, whether he would like to count each eighth note as a number or whether he would rather count every other number.