What is 0^0?

On desmos, if f(x)=x^x, f(0)=1. The function's domain is also restricted to x>=0. I do not know why since -1^-1 is -1 and -2^-2 is -1/4.
In school, I was taught that x^0=1 and 0^x=0 so why is one overriding the other?
So why is x^x restricted to x>=0 and why does 0^0=1?
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