Soon after you begin managing your first project, you learn that project management can be challenging. Even more of a challenge is managing one very large project or lots of smaller projects. Implementing master projects in Project can ease some of the burden.
Master projects are individual project files that contain other separate inserted project files. These inserted project files are called subprojects. This means that you can use one master project to view several small subprojects all on one screen. Each of the subprojects can be managed separately, either by you or by another project manager.
What's more, when subprojects are grouped into one master project, your filters, views, and reports will reflect the data from all projects combined. This allows you to see the “big picture” of your project management responsibilities in one place.