Fish oil is oil derived from fish like tuna, mackerel, herring, and salmon. It contains healthy omega-3 fatty acids in the form of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA).
Fish oil supplements are great for individuals low on omega-3 fatty acids. They're mostly used to support heart (healthy blood pressure and cholesterol), brain (learning and memory), and joint health (reduced swelling and stiffness).