WHAT IS A FUSE

Dear Student
A fuse is a small conducting wire made of special alloy that are of low melting point which protects the household electrical system from getting damaged by melting itself and thereby stopping the flow of current, due to unusual high current during a short circuit, power fluctuation in the electric line etc. 

The fuse wire is made of conducting alloy of very low melting point. It is rated according to the desired current required by an appliance. If the current is more than the rated value, the fuse wire heats up and melt to stop the flow of current. 

In short
A fuse is a safety device which prevents damages to electrical circuits and possible fires

Regards