Whatever you do in MPS, you do that in the context of a project. A project is an organizational unit that represents a complete software solution. It serves as a basis for coding assistance, bulk refactoring, coding style consistency, and so on.
A project in MPS is represented in the Directory Based Format. A project directory is marked with icon.
Such project directory contains the .idea directory, with the following files:
.iml file that describes the project structure.
workspace.xml file that contains your workspace preferences.
A number of xml files. Each xml file is responsible for its own set of settings, that can be recognized by its name: projectCodeStyle.xml, encodings.xml, vcs.xml, and so on.
Thus, for example, adding a new run/debug configuration and changing encoding will affect two different xml files. This helps avoid merge conflicts when the project settings are stored in a version control system and modified by the different team members.
All the settings files in the .idea directory should be put under version control except workspace.xml, which stores your local preferences. The workspace.xml file should be marked as ignored by VCS.
.idea directory is not visible in the Project view of the Project tool window.