Zoloft is a brand name for the antidepressant medication sertraline, which is a selective serotonin reuptake inhibitor (SSRI) used to treat a variety of mental health conditions, including depression, anxiety disorders, and post-traumatic stress disorder (PTSD). It works by increasing the availability of the neurotransmitter serotonin in the brain, which can help regulate mood and alleviate symptoms of these disorders.