Fuses and circuit breakers are safety measures designed to interrupt the power to a circuit when the flow is too great for the system to handle. For example, when your blow-dryer shorts out, the circuit breaker will trip. This protects the wiring in the walls from melting and a fire from starting.
The fuse contains a strip of metal that melts when the power exceeds the rated value. The metal causes the fuse to blow (or circuit to trip). A fuse must be replaced after it trips. A breaker on the other hand, is more complicated. Instead of melting, the wire bends, pulls the electrical contacts apart, and causes the breaker to trip. Each time a breaker is tripped, it is damaged a little. Eventually the breaker needs to be replaced.
