what is interrupt?

An interrupt is special signal which sent to the CPU to perform on it by the software and hardware. 

The processor respond by the suspending it's current activities, saving its state and executing a small program called an interrupt handle(or interrupt service routine, ISR) to deal with the event. 

This interruption is temporary, after the interrupt handler finishes, the processor resumes execution of the previous thread. 

Interrupt are basically two types-:

1-: External Interrupt

2-: Internal  Interrupt