Circuit Breaker is a device designed to open and close a circuit by nonautomatic means and to open the circuit automatically on a predetermined overcurrent without damage to itself when properly applied within its rating. They can be "tripped" (opened) thermally, by magnetic fields, or by external devices called "protective relays," depending on the design of breaker, its size, and the application. It serves as both swithch and overcurrent protection device.
Fuse is an over-current protection device with a circuit-opening fusible part that is heated and severed by the passage of overcurrent through it for the purpose of breaking a circuit in the event of excessive current. Fuses may be plug or cartridge type.
Cartridge fuse may be either ferrule or knife-blade.
Plug fuse screws into a base.