Neurons communicate via neurotransmitters released into the synaptic cleft, which bind to receptors on postsynaptic neurons.

“Neurons communicate with one another by releasing so-called neurotransmitters, which are just chemicals. Those neurotransmitters are vomited out, they're not actually vomited, but they're spit out into the so-called synaptic cleft, often called the synapse. The synapse is just a little gap between neurons. And when they are released into the synapse, they don't just stay there, they actually park or bind to receptors on what's called the postsynaptic neuron. And depending on how many receptors they bind to and how many receptors are available, et cetera, they can have a greater or lesser effect on the postsynaptic neuron.”