What is a Synapse
Neurons generally exchange messages when the sending neuron releases a chemical (neurotransmitter) which activates receptors in the receiving neuron. In most cases, neurons do not actually touch each other; instead, there is a tiny gap, called a synapse.
Neurotransmitter molecules may cross the synapse to activate a receptor on the receiving neuron, or may remain in the synapse unused until it is broken down or reabsorbed into the sending neuron to be recycled for later use.
by Catherine E. Myers. Copyright © 2006 Memory Loss and the Brain