Calculators vary from simple ones that just do add, subtract, multiply, divide, to ones that draw graphs, do statistical calculations, can be programmed, do conversions, etc. Some simple calculators have what looks like a tick (√). If this is what you mean, then you are talking about square root. If you multiply a number by itself you get another number. The square root of this other number is the number you multiplied by itself. So, for example, 5×5=25. So √25=5. Not all square roots are whole numbers. For example, √125=11.180...
If you see ∛125, this means “cube root of 125”. This is a bit like square root. If you multiply a number by itself and then by itself again you get another number. The cube root of this other number is the number you multiplied. For example, 5×5×5=125, so ∛125=5. The little 3 refers to the appearance of the three fives multiplied together.
I hope this explanation helps you.