There are many varied methods of steam cleaning your carpets.  The correct term for steam cleaning of carpets and upholstery is in fact "hot water extraction".  We will refer to it as steam cleaning as it most commonly known.

The most common form of steam cleaning is a 1 stage process, where a cleaner will bring to your home a portable machine

This steam cleaning machine is filled with water and detergent and your carpet is cleaned without any prespray or agitation.