Microsoft Project has many settings that control the behaviour of the application, and of your projects.
These settings can be accessed by clicking the File tab on the Ribbon and then Options. There are many useful options in here, but this blog post focuses on 5 MS Project settings you need to know.
Calculate Multiple Critical Paths in a Project
Although a project can only have one true critical path (the tasks that directly affect the finish date of the project). You may wish to view the critical path for each independent series of tasks.
This can be done to view the critical path for each subproject for a large master project, or maybe you have different independent series of tasks that are performed by different departments or regions in the project.