The openMSE packages use an object-oriented design. In essence this means that most functions take objects with an openMSE-specific class as arguments (e.g., OM) and return other objects with a different openMSE-specific class (e.g., MSE).
You can learn more about object-oriented design, although this isn’t required to use openMSE.
More important, is an understanding how the various openMSE objects relate together. This diagram shows how the various parts connect together.
The colors indicate:
yellow: openMSE objects
green: openMSE functions that operate on the openMSE objects
blue: features of the openMSE framework.
Clicking on various parts of the diagram will take you to the relevant pages that explain the objects, functions, and features in more detail.