Project resources
Resources are all folders and files existing in the Project either being under project root directory or linked from other location in your file system. The navigation views provide a hierarchical view of resources and allow you to open them for editing.
Linked Resources
Linked resources are files and folders stored in locations in the file system outside the project’s root directory. These linked resources represent additional files and folders you need for your successful build.
Path Variables
The path variables specify locations in the file system. They can simplify a process of adding project resources from commonly shared locations.
See also Path variables and Link to an existing file 'How to' chapters to learn how you can use path variables and linked resources in practice.