The whole product is one loop: you define a group of people, put a decision to them, and read back where they landed and why. Everything below is either part of that loop or part of knowing how far to trust it.
The shape of it
What you ask
The decision
Scenario, question & action space
The situation, the question, and the choices available.
If you read three pages
Simulation for what you are building, Result for what you get back, and Limits for what not to ask of it.
Where to go next
If you are setting up your first simulation, read Population, then Scenario, Question and Action space — those four are where accuracy is won or lost.
If you are deciding how much to trust a result you already have, read Confidence, then Validation and Groundedness.