text: Depends if you are asking about carpets or actual steam cleaning as used in industry.  Since you didn't say which I will answer both.\n\n1. Carpets.  Does not use steam but very hot water mixed with a solvent or detergent.  It uses pressure to make sure the solution penetrates deep and then vacuums the solution and removed dirt and hopefully grease into a holding tank for disposal.  A much cheaper and slightly more effective mixture than commercial cleaning fluids is real lemon juice.  The various acids naturally in lemon are a very effective grease cutter and also act as a fabric brightner.  Use the same amount as you would commericial cleaner.  (It can be used pure in a squirt bottle to degrease a dirty engine.  Spray on wait (the time it takes to spray should be long enough) and rinse or spray off.  I suggest spraying off with the same bottle.  That you won't get the wires wet and need to wait before starting the car.\n\n2. Industry.  Actually does steam and requires the user to wear a heat and waterproof suit.  The high temperature and presurre very effectively removes dirt and grease.  Usually it is used on machines heavily caked with grease.\n\nHope this helps