You sprained your ankle and are told to take ibuprofen to reduce inflammation. what is the mechanism of action for this drug?

Complex: Ibuprofen like all nonsteroidal anti-inflammatory medications inhibits the cyclooxygenase pathway in the formation of arachidonate acid and other pain mediating molecules. Interrupting this pathway the body does not form these inflammatory mediators and there's less signaling of inflammation which causes swelling and pain.

It is an inhibitor: It works by inhibiting the enzyme cyclooxygenase, which converts arachidonic acid to prostaglandin, which is converted by other enzymes(which are mediators of pain and inflammation. By blocking this pathway, you get pain relief and reduced inflammation.