The activities and tasks of projects should be designed to lead up to the creation of a deliverable. The deliverables are the major, concrete things that need to be done to create the new product or service the project will culminate in. So deliverables might include a project charter, the requirements specifications, designs and blueprints, intermediate product (e.g. a building that still requires insepection and completion), etc. I typically include deliverables as milestones in Gannt chart or other schedule documents. These milestones also become convenient group headings for tasks and activities in a WBS.