You can use different types of objects like folders, projects, summary tasks, tasks and milestones to help organize your plan.
A project contains tasks, summary tasks, and milestones. Projects live in the first layer of a plan. You can set a project's start and end date, which defines the bounderies of your project. If a project's task is not set to be completed before the project's end date, you will be automatically notified so that you never miss a deadline.
In more complex projects, it's useful to group tasks into structured sub-projects called summary tasks. Unlike projects, the duration of summary tasks is automatically set to the maximum duration of the tasks they contain.
To structure your projects in the overall planning you can use folders.