what does this mean? #if !(arch(x86_64) || arch(arm64))

I'm a newbie.

I came across this unusual code in a tutorial I was using.

#if !(arch(x86_64) || arch(arm64))
func sqrt(a: CGFloat) -> CGFloat {
return CGFloat(sqrtf(Float(a)))
}
#endif

It looks nothing like the code I've been learning so far. I know its a square root function but the hashtag? Something about my computer architecture?

Please explain it to me in simple terms.

Thanks