In C++, there’s often multiple ways to refer to the same entity: aliases, inherited names, injected names, names that differ in qualification… Usually, if an entity has multiple names, which one you use won’t matter: you can use any of those synonymous names and the compiler won’t care. But each entity always has a uniquely “truest” name, privileged above all the other ways to refer to it. In some situations, in order to do a thing with an entity, you do actually need to call it by its “true name.” Here is a (non-exhaustive) list of such situations.