Meta data vs Context Variables and how to use these

[MikeGoe]

Doc doesn't show difference between these very overlapping pieces - maybe more context around when to use which
Re:Meta tags - very difficult to understand how to "enable" - in Session Objects it states "auto enabled", but to retrieve, we still need to "activate" in policy or key tab.
List of available tags is missing.

[marksou]

@joshblakeley Can you have a look at this for me.