The Gayatri is one verse of the Rig Veda (3.62.10), ascribed to the seer Vishvamitra and addressed to Savitr, the sun as the impeller or vivifier. Its plain sense is a request that the worshippers may attain the adorable radiance of the divine Savitr, who impels their thoughts, a meditation on the sun's light asked to quicken and guide the mind. It is both a hymn and a mantra, and to force a choice between the two would misrepresent it: it functions as scripture, as the object of daily meditation, and as the initiatory formula par excellence.
In the classical scheme the Gayatri is imparted at the upanayana, the rite that makes a boy twice-born and admits him to Vedic study, and it is recited at the junctures of the day (sandhya) throughout life; the tradition treats it as the essence of the Veda distilled into a single verse. That immense sacred weight rests on a text whose surface is simply a prayer for the illumination of the intellect by the light of the sun. Modern reform movements have made it more widely available, extending its recitation beyond the groups and the gender that classical rules restricted it to, turning an ancient priestly formula into one of the best-known prayers of contemporary Hinduism.