Acetylcholine:

neurotransmitter essential to the production of movement through acting at neuromuscular junctions. Acetylcholine also has a number of functions in the central nervous system, and is thought to be involved in attention, memory, and a variety of other processes. The adjective cholinergic is often used to describe structures and/or activity associated with acetylcholine.

Watch this video to learn more about the neuromuscular junction: 2-Minute Neuroscience - Neuromuscular Junction