What is short circuit?

Hint: A short circuit is a type of a fault that occurs in a circuit. It is one of the reasons for overheating and can cause huge damages to the appliances connected in the circuit or can cause fires. Short circuits can be prevented by use of components that can detect it and break the circuit immediately.

Complete answer:
When a large amount of current flows through an unintended path, i.e. through components that were not supposed to be in contact with each other, in a circuit, then it is called a short circuit. The resistance in a short circuit is usually very low or there is very little opposition to the flow of a large amount of current. A short circuit can be very dangerous as it leads to overheating, fires or explosions. This can be prevented by introducing a fuse, circuit breakers or other overload protection in a circuit. A fuse is a metal wire with very low melting point like solder so when a large amount of current flows through the wire and the circuit starts heating up, the fuse melts and it breaks the circuit. It is usually present in our household electrical connections and prevents any damage to any appliance.
Nowadays, circuit breakers like MCBs are being used in place of fuses. Circuit breakers are switches which are designed to turn off when they sense the flow of a large amount of current or overheating. Unlike fuses which can be used only once, a circuit breaker can be used multiple times by switching it back on.

Note:
Short circuit occurs between two points which are at very high potential difference, for example- when we directly connect the positive and negative terminals of a battery together. The fuse wire can be made up of zinc, copper, silver, aluminum or alloys of tin and lead. MCBs are miniature circuit breakers.