The Task Hierarchy is the organizational system at the heart of Tasks.

You can create deeply task structures as needed at the level of granularity you want. Create a high level task like 'build a web site' and assign it to another team member. They can then flesh out the details under that top level task, assigning the individual tasks to other team members as needed.

The hierarchy is a very flexible structure shown in the Tree View you can use to organize your tasks they way you think about them.