Many people refer to a carpet cleaner as a “steam cleaner”. While steam cleaners do exist, these should be used for hard surfaces only. A steam cleaner uses actual steam to clean various types of surfaces, and this steam can damage carpet fibers and remove the protection. A carpet cleaner is designed to force a mixture of hot water and cleaning solution into the carpet to clean deep down. The solution and dirt are then extracted from the carpet, leaving the fibers and carpet base clean. So unlike actual steam cleaners, a carpet cleaner does not use steam.
Source - Bissell