The 3-4 defense is a popular formation used in American football, primarily by defensive teams. It consists of three defensive linemen and four linebackers. This setup allows for flexibility in both stopping the run and defending against the pass, as the linebackers can quickly adapt to various offensive plays. In the 3-4 defense, the three linemen typically focus on occupying blockers, freeing up the linebackers to make tackles or rush the quarterback. The four linebackers can be positioned in different ways, allowing for strategic blitzing or coverage, making this formation versatile and effective against various offensive strategies.