What is convolution operation? What's the use?

I don't know why many people answer such a simple question so complicated. Is it really that sentence? What is a professor? A professor explains a question that everyone understands so that everyone can't understand it. It seems that many students have inherited this tradition, which is the sorrow of education!

what is convolution and why is convolution used?

The reason is very simple. Any input signal can be regarded as the superposition of impulse signals, and the corresponding output can also be regarded as the superposition of impulse responses.

Is the superposition of impulse responses a convolution?

convolution is introduced because impulse is introduced, and the superposition of these impulse responses is convolution.