Most vexing parse c++ 11

Im confused about Y y {X{}}; what exactly this line does and where is connection to Most vexing parse , a brief explanation is appreciated

#include <iostream>

struct X {
  X() { std::cout << "X"; }
};
struct Y {
  Y(const X &x) { std::cout << "Y"; }
  void f() { std::cout << "f"; }
};
int main() {
  Y y {X{}};
  y.f();
}