There are 5 plans that differ in the amount of storage space (in GB) in the cloud. All plans include unlimited projects, tasks and users.

If you already know approximately how much storage space you'll need, it's best to select that plan from the start.
If you're just starting your first project, you can begin with the minimum plan and easily upgrade later when you need more space.
In any case, you have a 7-day free trial.