Serotonin is a neurotransmitter that plays a vital role in the central nervous system and peripheral nervous system, affecting various physiological and behavioral activities. It is synthesized from tryptophan, an essential amino acid, and is involved in functions such as mood regulation, cognition, memory, anxiety, sleep, appetite, and gastrointestinal homeostasis. Serotonin receptors are spread throughout the body, with different subtypes mediating diverse effects through various signaling pathways. Changes in serotonin levels have been linked to neuropsychiatric disorders such as anxiety, depression, and schizophrenia. Research on serotonin has shown its involvement in neural plasticity, cognition, happiness, and various neurological disorders. Understanding the functions and mechanisms of serotonin is crucial for the development of treatments for related conditions.