A rest is a period of silence. Small count numbers are placed under rests.
This symbol is a eighth rest. It indicates half a beat of silence.
When a rest comes after you have played a note, you must stop the note sounding: i.e., stop the strings vibrating (muting them). This can be achieved by placing your left hand fingers lightly on the strings. Do not press too hard as this will produce a new note. When using the left hand to mute a note, place the fingers flat over all four strings as this is easier than just muting one string (see photo). This muting technique is also useful to stop previously played notes sounding at the same time a new note is played.
The following two bar riff is played against a D chord and uses an eighth rest on the first beat of the second bar. The use of the rest gives the riff a syncopated feel. Syncopation means displacing the normal flow of accents, usually from on the beat to off the beat. In * time, accents normally occur on the numbered part of the count. By using a rest on the first beat, an accent is felt "off the beat", i.e., the "and" (+) part of the count.
Syncopation can be achieved by using either a rest or a tie.
Here is an example where syncopation is achieved by using a rest.
In this example the syncopation is achieved by using a tie.
The following riff uses an eighth rest and a tie.
The following progression is a Blues in A minor. Once again a syncopated feel is created by the use of eighth rests.