Worm gear pairs are an excellent design choice when you need to reduce speeds and change the directions of your motion, and they have many other applications as well.
Worm drives (or worm gear sets) are right angled drives and are used in screw jacks where the input shaft is at right angles to the lifting screw. Other forms of right angle drives are bevel gears, and hypoid gears. Worm drives satisfy the requirements of many systems and provide a compact means of decreasing speed whilst increasing torque and are therefore ideal for use in systems utilising e.g. lifting equipment where a high gear ratio implies it can be driven by a small motor.
A worm gear is a gear consisting of a shaft with a spiral thread that engages with and drives a toothed wheel. Worm gears are an old style of gear, and a version of one of the six simple machines. Basically, a worm gear is a screw butted up against what looks like a standard spur gear with slightly angled and curved teeth.
It changes the rotational movement by 90 degrees, and the plane of movement also changes due to the position of the worm on the worm wheel (or simply "the wheel"). They are typically comprised of a steel worm and a brass wheel.