Exponential form is when you expressed the product of the factor in an exponent.
By this, you make your equation shorter.
For example:
The product of the factor is 4, then you express it using exponent. That becomes 2^2
=> 2^2 = 2 x 2, which is equals to 4
Next, the product of the factor is 256, then you express it using the exponent. It becomes 2^8
=> 2^8 = 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2, which is equals to 256