The project tree is the backbone of your project. It allows you to structure the project and provides information about the project status. This gives you a wealth of information about your project at a glance. The following symbols are the most important for you:
Star symbol: You have overall responsibility for an element (see person responsible in profile).
Element, Folder or document symbol grey colored: By default, the tree is gray. The element is available for viewing, but you don't have responsibilites in that element.
Folder or document symbol blue colored: You are responsible for atleast one activity that is still in progress.
Open folder: The project or package is expanded in the project tree to display its subfolders.
Folder or document symbol green colored: All your activities (which you are responsible for) are finished.
Lock/Freeze: Next to the folder/document icon, there is a lock icon. This means that the item cannot be edited except by admins or owner (no adding of activities, customizing descriptions, changing dates, etc. is possible).
Aggregation paused: Instead of the traffic light, you will find a stop symbol (red, blue, or green). This means that the effects of the element is not included in the overall aggregation of the project.
Red Flag: Instead of the folder/document icon, you will find a red flag. This means that this item does contain at least one status report which was marked.