As per Wikipedia:

The Vedic texts are organized around four canonical collections of metrical material known as Saṃhitās, of which the first three are related to the performance of yajna (sacrifice) in historical Vedic religion.

  1. The Rigveda containing hymns to be recited by the hotṛ
  2. The Yajurveda, containing formulas to be recited by the adhvaryu or officiating priest;
  3. The Samaveda, containing formulas to be sung by the udgātṛ
  4. The fourth is the Atharvaveda, a collection of spells and incantations, apotropaic charms and speculative hymns.

The individual verses contained in these compilations are known as mantras. Some selected Vedic mantras are still recited at prayers, religious functions and other auspicious occasions in contemporary Hinduism.