c++ - What are rvalues, lvalues, xvalues, glvalues, and prvalues?

In C++03, an expression is either an rvalue or an lvalue.

In C++11, an expression can be an:

1. rvalue


2. lvalue


3. xvalue


4. glvalue


5. prvalue

Two categories have become five categories.

• What are these new categories of expressions?


• How do these new categories relate to the existing rvalue and lvalue categories?


• Are the rvalue and lvalue categories in C++0x the same as they are in C++03?


• Why are these new categories needed? Are the WG21 gods just trying to confuse us mere mortals?