What is meant by an electrochemical signal and where is it used?

Neurotransmitters are the chemicals in the body that control and regulate the body. An electrochemical signal appears at a neuromuscular junction (where the presynaptic axon terminal meets a muscle cell or motor unit). The term "electro" comes from the fact that anything happening within the nervous system and neurons is electrical signaling. The term "chemical" comes from the fact that once the neurotransmitters are released from the presynaptic axon and into the synaptic cleft and reach the muscle cell(s) the signaling becomes chemical due to the release of Ca2+.
I know, lots of science words but there's really no simpler way of describing it without it being even lengthier. If you have questions please feel free to email me, I can do my best to explain.