I understand how to square a number but I'm a little lost in my understanding as to why we would do it in certain circumstances?

For example.

If I take a number, say 20% and take another number 10% and divide 10 into 20 I get the figure 2.

You could liken this to an investment where the investment returns 20% and you would still keep that investment until it was returning 10% but not below. This would make 10% your minimum return. The resulting 2 would represent how many times the original value of the whole investment you would pay in order to achieve that 10% return. This is just hypothetical.

What would be achieved by squaring the 2 (making it 4). Is there some assumption to be made by squaring a number. If my question isn't clear then would anyone know if there is anything out there which explains the theory behind the reasons for squaring a figure and what is achieved. I often see this in maths but aren't sure what the reasons are for it.

Thanks.