when someone says a number squared or cubed, or to the certain power, it means how many times you multiply the base number by itself that many times, for example
2²= 2 * 2
or 9³ = 9 x 9 x 9
a square root or cube root, is a harder to understand, but still somewhat simple, it basically means how many what number squared or cubed equals this number.
so for example the square root of 9 = 3 because 3 x 3=9
or cube roots for example ∛125= 5 because 5 x 5 x 5
So here is an example one for you. √81.