A rest is a period of silence. Small count-numbers are placed under rests.
This symbol is a quarter rest. It indicates one beat of silence.
This black box is a half rest. It indicates two beats of silence.
If a rest comes after you have played a note, you must stop the note sounding. To do this, lift your finger off the fret but keep it lightly touching the string. To stop an open string sounding, lightly touch it with any finger of your left hand.
This song Aura Lee uses all the notes and chords you have learned so far. It also contains quarter and half rests. Remember to count as you play to help you keep time.