Omega-3 is called an essential fatty acid - because it essential in making healthy cell membranes and for your body to function well.
The main omega-3 fatty acids are EPA and DHA and, according to an article in the British Journal of Clinical Pharmacology, research has shown DHA and EPA reduce the process of inflammation, which has links to various cardiovascular and neurological illnesses.
Omega 3 can be obtained from fish oil or there is a vegan version extracted from flaxseeds with Alpha Linolenic Acid, which converts in the body to the Omega 3 fatty acids EPA and DHA.
Source National Institutes of Health Library
Effect of Omega-3 Dosage on Cardiovascular Outcomes: An Updated Meta-Analysis and Meta-Regression of Interventional Trials - PubMed (nih.gov)