An exponent is a number that shows how many times to multiply a number to itself.
For example, the expression

means to multiply x itself n times.
More examples.

= 5 * 5
We are going to multiply 5 itself two times. Because we have a two exponent.

= 8 * 8 * 8
8 is being multiplied by itself 3 times because the exponent is 3.
So, that is what exponents are.