Properties
Each property is its own record — settlement date, ownership, loan, and everything you've imported against it — and your portfolio view is the sum of all of them.
Every property you add becomes its own record: address, settlement date, ownership structure, loan details, and every transaction and document you attach to it from there. Your portfolio view is a roll-up of every property you've added, so the accuracy of the portfolio-level figures depends on each property being set up correctly to begin with.
Editing a property
Purchase details, loan terms and ownership can all be updated later from the property's own page — useful when you refinance, or when a fixed-rate period ends and the rate changes.
Selling a property
Recording a sale keeps the property's full history in your reports rather than deleting it, which matters for CGT — you want the record of what you paid, held and claimed, not just a clean slate afterwards.
See adding your first property for what each setup field feeds into.