What's the difference between Laser Diode, LED and Lasers?
Laser is an acronym for basically a light beam with a very small spread. Lasers come in a multitude of forms from chemical to electrical to gas. Not all are diodes, not all are semiconductors.

LEDs on the other hand are semiconductors, and are always diodes. Unlike most diodes, leds can't be run in reverse without precise amperage control. 

Another big difference is the power. Most leds (with the exception of high output) are more efficient than their laser counterparts.