Difference between add_lvalue_reference_t

Suppose you have a template argument T.

What are the differences between

• add_cv_t<T> and const volatile T
• add_const_t<T> and const T
• add_volatile_t<T> and volatile T
• add_lvalue_reference_t<T> and T&
• add_rvalue_reference_t<T> and T&&
• add_pointer_t<T> and T*?

Why should I use add_rvalue_reference_t<T> instead of T&& for example. Are there any rules when to choose which?