A connection between two neurons. It is a site where memory is effected by changes in conductivity. If a synapse is facilitated, nerve impulses flow easily from one neuron (nerve cell) to another. If it is depressed, flow of information is suppressed.
While neurons transport information electrically, the information is transported over the synaptic gap chemically via neurotransmitters. The neuron that sends the information releases neurotransmitters into that gap. The neurotransmitters are then recognized by receptors on the surface of the recipient cell, which upon this stimulation in turn relays the signal. About 10% of the neurotransmitters are lost in this process, the other 90% are released from the receptors and taken up again by the sending cell (thus reuptake).
The function of this mechanism can be altered by chemicals. These can be produced by the body (e.g., endorphines), but also be man-made like drugs (e.g., nicotine or heroin) or anti-depressants (e.g., SSRIs).