Zamboni is a manufacturer of ice resurfacing machines.  Calling one a Zamboni is like calling a tissue a Kleenex or calling an adjustable wrench a Crescent wrench (genericized trademark).  Ice resurfacing machines work like this:

1.  A blade scrapes a layer of ice off the surface.
2.  An auger gathers the scraped ice and puts it into a bucket.
3.  Hot water is sprayed onto the ice to remove dirt and debris.  Hot water is used because it "loosens the crystal structure of the old ice underneath, so the new ice will form a solid bond with the old ice, instead of a separate layer that chips off easily."
4.  Excess water is squeegeed off with a rubber blade and then vacuumed up. 
5.  Warm water is pumped out along the squeegee blade and spread evenly over the ice. 

Charlie Brown said it best: "There are three things in life that people like to stare at:  a flowing stream, a crackling fire, and a Zamboni clearing the ice."