Synergist Versus Antagonist in Muscles

The term synergist refers to muscles that work together with another muscle to achieve a desired goal. For example, the biceps and the brachialis work concurrently (or synergistically) in the movement of the elbow during flexion.

the term antagonist referst to muscles which act in opposition to eachother. For example, the bicept and the tricept work in opposition of eachother.