The flam is a distinct sound created by two successive drum strikes made by the two sticks. It is essentially a way to embellish any given note and play it in a “fancier” fashion.
The flam consists of a main note, made by the second stick that hits the drum, and a preceding grace note that’s played right before it. The main and grace notes must be played a small fraction of a second apart, or they will sound like two separate notes. They must also not be played too close together or both sticks will essentially strike the drum at the same time resulting in an ugly, choked sound.
The flam is another standard snare drum rudiment. As a rudimental exercise, it is played with alternating hands. First the flam is played with a left hand grace note (the 1st note) and a right hand main note (the 2nd note), then with a right hand grace note and a left hand main note, and so on like so:
Here the small superscripted letter represents the grace note, and the larger letter the main note.
Of course, this pattern can also be started with the role of the hands reversed:
The key to playing a good flam, in which the two strikes are neither too far apart, nor simultaneous, is to start each hand’s drum stroke from a different height. The hand striking first, starts a few inches off the drum, while the one striking second starts considerably higher up, and therefore will arrive at the drum’s head a bit later. The grace note will be played from a lower height, and therefore will be weaker, as it should.
When playing the alternating hand rudiments, the hands switch roles each time. So for each flam, the stick playing the main note should not be allowed to bounce high up but rather stay close to the drum to prepare for the grace note, while the stick playing the grace note should be raised up after it hits to prepare for the main note.