Compilation and execution when code is not dislosed; use of ellipsis in code

In an interview I was asked following question

Given the code fragments below, where the ellipsis (…) represents code that has not been disclosed to you:

class X { … };  class Y { public: explicit Y(const X& x); … }; 

what can you say about the compilation and execution of each of the following statements? Describe each of the operations that occur as this code executes.

Y func(Y y) { … }
X x;
Y y = func(Y(x));

I could not understand the question properly hence was not able to answer. if some one could explain me what answer was expected of me or share any link which I can go through, that would be really nice. Many Thanks.