Square root just means what number when multiplied by itself makes that number. So, the square root of 25 is just 5X5, since 5X5 = 25.

I just use a calculator to find it, but you can do it manually too. So, for example, if you want to know the square root of 20, we can use the fact that we now the square root of 25 = 5 and 16 = 4, so the square root of 20 is between 4 and 5. Just guess numbers and see how close you can get by trying them out by multiplying them together. Best to just use a calculator for things that are not whole numbers.