This is a sixteenth note.
It lasts for one quarter of a beat.
There are four sixteenth notes in one beat.
There are 16 sixteenth notes in one bar of * time.
Count out loud as you play this example and remember to keep all the notes even in length and volume. Tap your foot on each beat and be careful not to tap in between the beats.
Here is a Funk riff which makes use of sixteenth notes.
As with other beat subdivisions (e.g. eighth notes and triplets) it is important to be able to play all your scales and arpeggios using 16th notes. Here are some examples. The first one is the F Blues scale over two octaves.
This one shows the arpeggios of D major and D minor played in 16th notes.