why do we use the word vacuum? is a vacuum created inside the appliance?
Fan blades turned by a motor create a suction (partial vacuum' inside the machine which sucks up the dirt. It's similar to you drinking a liquid with a straw. You stick one end of the straw into the liquid and suck on the other end. You create a vacuum inside the straw and it sucks up the liquid to fill the empty space (vacuum).
