The estate agent rang. Your offer was accepted: £200,000 for a two-bed flat. You have £20,000 saved as a deposit. That means you need to borrow £180,000. Four mortgage products are on the table. They look similar today. In five years, they won't.
A mortgage is the largest single borrowing decision most people ever make. Choosing the wrong product at the wrong time can cost thousands of pounds a year. There is no one right answer. What's right depends on what rates do next, and nobody knows that for certain. The skill is understanding how each product behaves, so you can make a choice that fits your situation.
In the real world, no one knows what rates will do. To learn how each mortgage behaves, pick a scenario. Or hit "surprise me" and find out at the end of the sim.