to shine or give light: for light to break out, or for something to send light out onto what was dark
This verb is the action behind light. In its simplest form it describes light arriving on its own: morning breaks, day grows bright, a path gets clearer as the sun climbs. Used that way it is about a scene lighting up, with no one named as the source.
More often the verb is causative: someone or something makes light fall on what was dark. The sun, moon, and stars are set in the sky to give light to the earth; a lamp throws light across a room; the pillar of fire lights Israel's way through the night. The same word covers the spark of kindling a fire and the flash of lightning that lights up the whole world.
From there it turns figurative without changing its core. To enlighten someone's eyes is to revive them, to bring them back from the dimness of exhaustion or death. Above all, for God to make his face shine on a person is to turn toward them in favor and life, the picture at the heart of the priestly blessing. The connection holds throughout: whether literal daylight or the warmth of God's regard, the word names light reaching what was dark.
A related shade describes the result of all this, being radiant or being given light: God himself is radiant with majesty, and a person can be enlightened with the light of life.