To support move operations, the new standard introduced a new kind of reference, an rvalue reference. An rvalue reference is a reference that must be bound to an rvalue. An rvalue reference is obtained by using
&& rather than
&. As we’ll see, rvalue references have the important property that they may be bound only to an object that is about to be destroyed. As a result, we are free to “move” resources from an rvalue reference to another object.
Recall that lvalue and rvalue are properties of an expression (§ 4.1.1