This type of user can view and add items to all folders, documents, calendars and projects of the workspaces to which they are assigned, but cannot modify or delete items that they did not create. An Contributor can upload new versions to any document in Documents, whether or not they uploaded the original version.
An Contributor cannot create new workspaces or users, nor can they view/edit Reviewer or Partner user information.
In Projects, an Contributor can add a task (but not a project) and can edit tasks to which they are assigned. They can upload an attachment to any project or task to which they have access, whether or not they are responsible.