Hang around a gym long enough, and you’ll probably hear talk of compound versus isolation moves. It’s pretty self-explanatory: Compound exercises recruit multiple muscle groups (squats, for example, recruit your glutes, hamstrings, quads, and even your core for stability). On the other hand, isolation movements zero in on just one muscle (like the leg extension machine).
Both forms of exercise have merit, depending on your individual goals. But frankly, we like compound moves because they work more muscles in less time. (And who isn’t time-crunched these days?)