Neurotransmitter:These are endogenous chemicals that enable neurotransmission. They transmit signals across a synapse from one neuron (nerve cell) to another 'target' neuron.
Synaptic Cleft: This is a gap between two nerve cells which forms a junction for transmission of nerve impulses through release of neurotransmitters.
Receptor Site: This refers to specific areas on dendrites or neurons designed to receive specific neurotransmitters. It's similar to how only certain keys can open certain locks.