Blown fuses must be replaced after they blow. The fusible link is melted within and the connection link is no more. However, with circuit breakers, they have a resettable switch that once again makes the circuit breaker both functional and a viable circuit protector.
Fuses come in different shapes and sizes. There are plug and cartridge fuses. But the question remains, why do fuses blow? And while we're on the subject, how do you test the fuses? I have my opinion on which is better, which is most effective, and why. I'm wondering what your thoughts are about the subject. You can voice you thoughts in my poll on fuses or ciurcuit breakers.
Circuit breakers are resettable in most cases, as long as they haven't become damaged or the circuit problem that created the breaker to trip in the first place is now clear. If a circuit breaker does trip, here's how to reset it. However, if the circuit breaker is bad and needs replacement, here's how to remove and replace a circuit breaker. To do this, you'll need to know how to turn off a circuit breaker. This circuit breaker may be a single-pole breaker or a double-pole breaker. Here's a rundown of circuit breakers that are used in circuit breaker panels.
I hope all of the information that I've provide you in the links above paint you a picture of what fuses and circuit breakers are, how they work, and which is for you. I'll leave you with this final link covering fuses and circuit breakers.