Inflammation is the body's protective response to injury or infection that involves immune cells, blood vessels, and molecular mediators. It causes redness, heat, swelling, and pain. There are three phases: acute, delayed, and chronic. Mediators like prostaglandins and histamine cause vasodilation, increased permeability, and pain. Steroidal anti-inflammatory drugs and non-steroidal anti-inflammatory drugs inhibit inflammation by different mechanisms. NSAIDs inhibit the COX enzyme to prevent prostaglandin production, while steroids inhibit phospholipase A2. Both drug classes can cause side effects with long term use like gastric irritation.