Most people are familiar with the basic circular saw, sometimes called a "skillsaw," though that is a brand, as when one refers to tissue as "Kleenex." These saws are constructed with a pistol-type grip to the rear, and a trigger-button which activates the saw.
Another popular type of saw is the "worm drive" or "framing" saw. This saw is a variation on the circular saw, which is designed to fit in smaller spaces; the motor is at the back. Because there is no motor beside the blade, the saw's width when viewed from the front (the direction of the cut) is much smaller.
These saws, as other tools, are manufactured to varying levels of quality and durability. The plastic ones such as DeWalt are lighter, and for framers cutting in a bent over position that is good! However they do not take well to drops or impacts. A sturdier tool would definitely be one with a metal body such as Ridgid or Makita, though these models are noticeably heavier.