Neurons communicate with each other at synapses.
Synaptic transmission takes place through the release of small amounts of transmitter substances from the nerve terminals from a presynaptic neuron into the synaptic cleft.
The transmitter crosses the cleft by diffusion and activates or inhibits the postsynaptic cell by binding to a specialized receptor molecule.
In a few cases, retrograde transmission may occur from the postsynaptic cell to the presynaptic neuron terminal and modify its subsequent activity.