There are 10 plans that differ in number of projects available and free space in the cloud. All projects have unlimited tasks in each project and unlimited users.
If you already know the exact number of projects, choose the one that suits you. If you are starting to work on your first project, you can choose the 1-project plan and if you are going to increase the number of projects in the future, you can switch to the right one.
In any case, you have a 45-day free trial.