Typical SCORM learning environment. An LMS is the central hub of the learning environment, delivering content and recording learner progress.
The LMS continues to be the central hub, but learner progress is also sent to a LRS via xAPI. The dual tracking of learner experiences provides a consistent means to access that data for uses such as reports and analytics.
The reliance on the LMS has diminished. The LRS stores learner experiences and content no longer needs to be managed by the LMS. At this point, the LMS, if used, is just a consumer of the xAPI service.
A services based approach to training and learning environments. APIs for learning services are defined and used to create a a completely customizable training and learning environment.