A synapse is a junction between two neurons or between a neuron and another type of cell. It allows for the transmission of electrical or chemical signals. In chemical synapses, neurotransmitters are released from the presynaptic neuron into the synaptic cleft and bind to receptors on the postsynaptic neuron, facilitating the communication between nerve cells. This process is essential for neural communication, influencing functions such as reflexes, muscle contractions, and sensory perception.