What does this line mean. (::*) [duplicate]

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• About meaning of ::* on this code [duplicate] 1 answer

While refactoring a piece of code I came across the line below:

class Bar
{
protected:
    int (Bar::* fooFunction)(float); //this line
}

I have never seen this kind of syntax before. What is this syntax and why is it used it used in C++?