A swing operator is used when a gate (or two gates) open inward or outward away from the wall. Similar to your bedroom or bathroom might, simply opening inward or outward.
Swing gate openers can use three types of operators. A swing arm operator, which is a box, that sits off to the side and has an arm extending to the gate. A ram arm is located on the gate and post and uses either a hydraulic piston or a jackscrew-operated piston. Underground operators are located by the hinge and operate the gate via a link arm. One item to consider is how often your gates will open and close. Usually it is a minimal cost to upgrade to a heavy duty gate opener or operator.