Both devices, either breaker or fuse, are designed to trip (turn off) in the event of an electrical overload, i.e. 20Amps of electrical load on a 15Amp circuit would cause a trip. The only difference is that a breaker is mechanical and may be reset. Whereas, a fuse is one time only and must be replaced. Please Note: Modern breakers are much more efficient and offer greater levels of protection. They are easy to visually tell apart as the circuit breaker panel has small switches inside which are labeled to show which circuit belongs to which switch.
Fuse panels used to be popular in home construction but they are not used very much any more. Most new homes now utilize breaker panels. A fuse box utilizes small circular fuses instead of the switches in a breaker panel and they need to be replaced before the circuit may be used again. Fuse panels also offer a limited amount of power and often do are not able to power simple electronics or appliances.