The Open edX Platform is a web-based system for creating, delivering, and analyzing online courses at massive scale. It is the software that powers edx.org and many other online education sites.
There are a handful of major components in the Open edX project. The primary component is edx-platform, which contains the learning management and course authoring applications. Where possible, components communicate using stable, documented APIs.
For more information about Open edX platform architecture, please refer to the Open edX Developer's Guide.