Wand-Lighting Charm

Lumos is a spell that causes the tip of the caster's wand to light up, pretty much a "wizard's substitute" for a Muggle torch (a.k.a. flashlight). Evidently the light is a flame of some kind, because Alastor Moody burned a piece of paper in it in Harry Potter and the Order of the Phoenix. The spell was first used in Harry Potter and the Chamber of Secrets.

More powerful versions of this spell are, Lumos Maxima which is performed by Harry at the Dursley's house in the Harry Potter and the Prisoner of Azkaban film and Lumos Horlem used in ''Harry Potter and the Philosopher's Stone (film)

The spell to extinguish the light is Nox.