This option is used to save all the project models back to the disk, not just the project.
Continue down the page to see the Save All Models Panel options.
To view the Save all Models Panel, Use: Models => Utilities => Save => Save All Models
Hit the <Save> button to save all the unsaved models in the project.
Note: Models are automatically saved on the disk when they are first created, but various operations can then change the data in the models which may not be immediately updated on the disk. This option the ensures that the models will be saved to the disk, ie server location, or local disk ie C: drive. It is like exiting and saving the whole project back to the disk, but this panel will save all the models in the project to the disk location.