Build a glossary for this domain

New starters keep asking what a word means and getting three answers.

Build a glossary from the material below.

For each term:
- A one-sentence definition a newcomer understands without following a link
- A second sentence only if the term is easily confused with another. Name the other and give the distinction
- Where it appears in our system: the table, the service, the UI label
- Any term used differently here than in the wider industry, flagged explicitly

Also produce two lists:
1. **Collisions**: terms used for more than one thing, or several terms used for the same thing. Recommend which usage wins.
2. **Undefined**: terms that appear in the material without ever being defined anywhere.

Define terms in dependency order where one definition needs another, but do not create chains longer than two.

Material (docs, code, tickets, or a transcript):

Getting someone started. READMEs, setup guides, onboarding and glossaries for the person meeting this for the first time.