Roots are the number that when multiplied by itself creates that number. If you were looking for the square root of four - Square root being the number that when multiplied by itself equals that number, you would find it to be two.
So the square root of four is two.
The cube root of a number would be the number times itself three times that equals that number. For example the cube root of 8 would be two since 2x2x2=8 or 2x2=4 2x4=8.