The Four Vedas:

1. The Rigveda, containing hymns to be recited by the hotar, or presiding priest;
2. The Yajurveda, containing formulas to be recited by the adhvaryu or officiating priest;
3. The Samaveda, containing formulas to be sung by the udgatar or priest that chants;
4. The Atharvaveda, a collection of spells and incantations, apotropaic charms and speculative hymns.

Source: Vedas, Wikipedia: The Free Encyclopedia