The MathExtensions project is created automatically if it does not exist already. The MathExtensions project is the project that should be used to develop theories that can be used by all projects. Other theories that may not be useful to all projects, but to a specific one, should be created within that project. Those theories are said to be project-scoped.
Workspace Scope: Refers to the theories that reside in MathExtensions project. Deployed theories in this project are available to the entire workspace.
Project Scope: Theories that are not in MathExtensions are project-scoped, and are only available within the parent project.