From Wikibooks

This diagram shows the seven different types of rests used in muscical notation for pianos.

1. The rest with the 1 underneath is known as a whole rest. This name is easily remembered with the fact that the rest drops under the line on the staff, making it a "hole". This rest takes up four beats of music, the size of the standard measure.

2. The rest with the 1/2 underneath is known as a half rest. It constists of two beats, generally half a measure.

3. The rest with the 1/4 underneath it is a quarter rest. It consistes of one beat, or one fourth of a standard measure.

4. The rest with the 1/8 underneath is known as an eighth rest. it consists of 1/2 of a beat, or 1/8th of a standard measure.

5. 1/16- 16th rest. 1/4 of a beat, 1/16 of a measure

6. 1/32- 32nd rest. rarely used. 1/8th of a beat, 1/32nd of a measure

7. 1/64- 64th rest. rarely used. 1/16 of a beat, 1/64th of a measure.

The 1/32 rest and 1/64 rest are rarely used in most pieces, with the exception of some slow pieces or pieces with irregular time signatures.