There are three different types of resources that exist in the workbench.
File resources in the workbench are synonymous with files as you see them in the file system.
Folder resources in the workbench are synonymous with directories on a file system. In the workbench, folders are contained in projects or other folders. Folders can contain files and other folders.
Projects can contain folders and files. Projects are used for building, version management, sharing, and organizing resources.
When you create a project, you indicate a file system location for the project. If you browse to this location in your file system explorer, you can view the project and its contents.
A project is either open or closed.
When a project is closed, it cannot be changed in the workbench. The resources of a closed project will not appear in the workbench, but the resources still reside on the local file system. Closed projects require less memory. Since they are not examined during builds, closing a project can improve build time.
When a project is open, the structure of the project can be changed and you will see the contents.