An exponent is a number written above and to the right side of a value or number in math. The value or number is called the base, and the expression is read out as;
"Base raised to the power of exponent."
An example is given below;

In this example, 10 is the base and 3 is the EXPONENT.
The expression is now read out as,
"10 raised to the power of 3"
Note that even unknown values (such x as we commonly use in math) can also be an exponent or base. For example, we can have;

So basically, an exponent indicates the number of times a number is used to multiply itself.
If the question is 5m^2 the answer is 80. And if the question is 5m2 then it is 40
9 decimeters. deci = 0.1
9 *0.1 meters.
0.9 meters
9 decimeters = 0.9 meters.