Details
Using a redstone torch as a source of light is not recommended because it has just half the light output of a regular (coal) torch. Redstone torches will not melt ice or snow due to their low light level (7), and will not prevent mobs from spawning.
A Redstone Torch can provide a power source for wires. Wires in turn are used to operate doors, pistons or switches from a distance. The torch can power the wire for a length of 15 blocks, and takes 1 tick in Minecraft world time (approximately 0.1 seconds) for power to flow through it.