Hello.
It is the number that when you multiply it by itself gives 80. So, the square root of 9 is 3 since 3 x 3 = 9.
It’s not a whole number though, since 8 x 8 = 64 (too low) and 9 x 9 = 81 (close, but too high).
It is very close to 8.9442719099991587856366946749251, but it is known as a surd, and can not be written exactly as a decimal (it goes on forever, and doesn’t repeat) or a fraction.
Have a nice day