This is an eighth note. It lasts for half a count. There are eight eighth notes in one bar of * time. When eighth notes are joined together the tails are replaced by one beam.
The following example shows a constant stream of eighth notes played on the snare drum. Alternate the hands RLRL and then reverse them (LRLR). Once you can do this strongly and evenly at a reasonable tempo, play the example with one hand at a time (RRRR etc and LLLL etc). Once again, remember to count out loud as you play.
The next important step in gaining control of eighth notes is to play them on the hi-hat and ride cymbals with the right hand as demonstrated in the following example. It is important to keep the notes even and the sound consistent.
Once you are comfortable playing eighth notes with the right hand, try adding the some notes on the snare drum with the left hand as shown here.
It is also worth practicing eighth constant notes on the bass drum as shown in the next example. This will develop the endurance of your leg muscles and give you more control when playing beats containing eighth notes. Practice this one for short periods at first. Once again, the aim is to get all the notes to sound consistent in volume and time.
The next step is to play eighth notes on the hi-hats or ride cymbal and add the bass drum in various positions on or between the beats. Work on this until you can do it easily.