As a developer, you build XBlocks that course teams use to create independent course components that work seamlessly with other components in an online course.
For example, you can build XBlocks to represent individual problems or pieces of text or HTML content. Furthermore, like Legos, XBlocks are composable; you can build XBlocks to represent larger structures such as lessons, sections, and entire courses.
A primary advantage to XBlocks is that they are sharable. The code you write can be deployed in any instance of the edX Platform or other XBlock runtime application, then used by any course team using that system.
By combining XBlocks from a wide variety of sources, from text and video, to multiple choice and numerical questions, to sophisticated collaborative and interactive learning laboratories, course teams can create rich and engaging courseware.
You must design your XBlock to meet two goals.
XBlocks are like miniature web applications: they maintain state in a storage layer, render themselves through views, and process user actions through handlers.
XBlocks differ from web applications in that they render only a small piece of a complete web page.
Like HTML <div> tags, XBlocks can represent components as small as a
paragraph of text, a video, or a multiple choice input field, or as large as a
section, a chapter, or an entire course.