A switch is a hub where every port can act as a bridge. The switch as a whole keeps a master list of all these MAC addresses by port. It periodically drops un-seen addresses from its list, this period can often be specified. If the computer on port 2 is sending a huge file to the server on port 8, no other ports see this traffic. Network traffic problems almost always disappear with switches.
Collisions become a thing of the past.
From our tests, users on a switched 10Mbit network see about as much of an increase in network speed as users on a shared 100Mbit network from the reduction in collisions alone. Users on a switched 100Mbit network are, of course, spoiled.