Lums (pronounced “Looms,” like ilLUMination, and not Lums, for dumb) are beings of pure energy possessed of a mindbogglingly sunny disposition. They are an important source of magical energy in the Glade of Dreams, making Lums Racing a popular Gladewide sport. The competition pits up to four players against each other in crazy crosscountry competitions to collect Lums. Anything goes in this wild race, or as we say around here, no smack is too packed. While all players go home winners, only one takes the prize: the player who nabs the most naphappy Lums, of course! No holds barred!—Official site, Rayman Origins
Lums can be quite illuminating, for those who know how to use their energy...
A Lum is a small body (or shard) of magical energy which is found in the Rayman games starting from Rayman 2. Generally, there are six different types of Lums that are determined by colour, though in Rayman 3 there is the existence of Black Lums. They usually appear as small lights with insect-like wings, though in Rayman M and the Game Boy Advance version of Rayman 3, Lums look like crystal balls. The name is derived from the French word 'lumière', which means 'light'. Lums in Rayman Kart look like piles of gold money and there are roughly two million of them.
In Rayman Origins, Lums return with their winged form, and are a significant source of energy in the Glade of Dreams. However, Lums are no longer divided by types or colours, as they all resemble Super Yellow Lums with arms and legs, and turn red when a Lum King wakes them up to start dancing. In their red condition, Lums turn hot, and their energy duplicates. The Magician is interested on the power that he can extract from the Lums, and in order to make an exchange, players must collect a certain amount of Lums for the Magician (measured by a test tube) to adquire some Electoons. If players reach the limit of the test tube, they will obtain a Lum Medal. In this game, Lums seem to be infinite, as there can be more than 350 Lums in almost every regular level.