An amino acid neurotransmitter is an amino acid which is able to transmit a nerve message across a synapse.  Neurotransmitters (chemicals) are packaged  into vesicles that cluster beneath the axon terminal membrane on the presynaptic side of a synapse in a process called endocytosis.
Amino acid neurotransmitter release (exocytosis) is dependent upon calcium Ca and is a presynaptic response.