The Rig Veda opens with Agnimile, which means ‘I praise Agni (Lord of Fire),’ who is seated before my eyes. Agni, or fire, symbolizes the light of spiritual knowledge leading one to Truth.
Agni is nothing other than the innermost light that shines in all animate and inanimate as the Self, as inner consciousness.
Rig is derived from the root ‘Rc’ meaning ‘to praise.’ The Rig Veda is made up of hymns in praise of the Divine. The great sages of yore are said to have perceived the eternal truth, and bequeathed to posterity their apprehensions of the numinous. These sagely revelations came to be known as Vedas, of which there are four: Rig, Yajus, Sama and Atharva.
Source - My Mother, My Master By Swami Pranavamritananda Puri