A project is a named group of tasks — "Q3 launch", "Home renovation" — with its own page. Projects can be personal (just yours) or belong to a team; personal projects are free on every plan.
You can build a project from scratch, or start from a template — a ready-made set of sections and tasks for something common (like planning a trip or a launch), which you can edit freely afterward.
Deleting a project never deletes its tasks. They fall back to your main task list, unfiled, so nothing is lost by reorganizing.