I'm torn about this, since there is good content here. But ultimately I think
* This page is a lot of work to write and maintain.
* In most cases, the right thing is for people to find the page that
explains the full feature. E.g. if you don't know what an "administrator"
is, the page I hope you find is "Roles and Permissions". For bots, it's
"Bots and Integrations". Writing a punchy short summary for a glossary
that does better than that is possible, but not fast.
* People find things via search, e.g. by Googling "What is X in Zulip",
rather than looking for a glossary.
* This page was written more than 3 years ago, before we had 100+ help
articles. So it may have served a purpose in the past that no longer
exists.