There are certain pieces of equipment that are needed in order to SCUBA dive

Regulator

The regulator is the most important piece of equipment that a diver can have. This is the piece that conects to the air tank and let you breathe underwater.
It also has conneted to it dials that that show how much air is left in the tank and how deep you are currently located under water. It also connects to the next piece of equipment to provide the air to ascend and descend under water

BCD (Bouyancy Control Device)

This is the device that lets you make a controled descent or ascent under water. It is most offen in a 'jacket stye', however; technical divers tend to prefer a padded air pocket on their backs known as a 'wing'. It is connect to the regulator by a hose and has a control that lets you dump or add air to the BCD depending on if you want to go up or down.

Exposure suit

This is what most people would call a wetsuit. However; in divining there are wetsuits for warm water, semi-dry suits for colder water and drysuits which are worn with layers underthem for very cold water.

Weights and weight belt

As the human body is naturally designed to float, a weight belt threaded with blocks of lead is word to counteract this tendency to float.

Mask

A mask is worn to so divers can keep water out of their eyes and to see clearly underwater.

Fins

Fins are worn on the feet to help divers propel themselves along underwater. These can range from fins you just slip your foot into, to ones that must be worn with boots.