Context Operations

Hi Everyone,

                 I'm new to webdynpro abap. I want to know the context operations & attributes

                with simple examples. Could anyone suggest me some examples for the following things.

                   1. Read

                   2. Set

                   3. Append

                   4. As table operation

                   5. wd_this

                   6. wd_context

                   7. wd_comp_controller

Thanks in advance.