A gate motor (also called a gate operator) turns a gate you push by hand into one that opens by itself. A sliding gate uses a motor on a pad that drives a toothed rack. A swing gate uses an arm fitted between the post and the gate, or a motor hidden in a box under the hinge.
The big-three brands in Australia are CAME, Beninca, and FAAC, with Centsys, Nice, and Centurion also widespread. Sizing depends on gate weight and duty cycle. A residential single sliding gate up to 400 kg runs on a CAME BX704 or equivalent. Heavy commercial gates 1000 kg-plus need industrial duty drives like a CAME BY3500.
Every motor needs safety devices on the safety circuit (photo eyes, safety edges) plus a manual release for power failures. Australian Standard AS/NZS 4505 covers the safety requirements for automated gates.