Universal reference parameters often have efficiency advantages, but they typically have usability disadvantages.

Overloading on universal references almost always leads to the universal reference overload being called more frequently than expected.

But don’t apply std::move or std::forward to local objects if they would otherwise be eligible for the return value optimization.

If a function template parameter has type T&& for a deduced type T, or if an object is declared using auto&&, the parameter or object is a universal reference.

std::move performs an unconditional cast to an rvalue, while std::forward casts its argument to an rvalue only if that argument is bound to an rvalue.