One of the unique features of CompleteProject is the ability to delegate tasks and projects to other users. The easiest way to see how this works within CompleteProject is to work through an example.
Let's say you're the CEO of ABC Corporation. As a small part of your responsibility for the year you need to manage the marketing for ABC Corporation. To do this you create a new project called "Marketing". Under the Marketing project you create a subproject called "Create Marketing Plan". Now - you don't want to create the marketing plan because you have other things to worry about. So you delegate the "Create Marketing Plan" project to your vice president of marketing. At this point one person has access to the marketing project and two people have access to the "Create Marketing Plan" project.
Your VP of marketing decides that market research will be necessary before creating the marketing plan. He therefore creates a new project under "Create Marketing Plan" called "Market Research". The "Market Research" project is then delegated to an outside firm. At this point one person has access to the marketing project, two people have access to the "Create Marketing Plan" project and three people have access to the "Market Research" project. In this sense permissions are hierarchical and automatically applied. Note that as the owner of the "Marketing" project you can see everything that is going on with the "Market Research" project even though your vice president of marketing has not made you aware of his intentions to hire an outside firm. In other words your vice president of marketing is in complete control of the project but you have visibility should you choose to go into the detail. Also note that the outside firm cannot see "up" the hierarchy. They can only see the project which they have been delegated - "Market Research". Therefore secure company documents can be safely placed in parent projects - the only people who have access to such documents are the people who have access to the appropriate project or parent project.
Such a hierarchy of permissions and delegations can go on indefinitely. Such that the CEO of a company could in theory see what everyone in the company is working on and how that relates to the larger goals of the company.