The XBlock SDK is a Python application you use to help you build new XBlocks. The XBlock SDK contains three main components:
An XBlock creation tool that builds the skeleton of a new XBlock.
An XBlock runtime for viewing and testing your XBlocks during development.
Sample XBlocks that you can use as the starting point for new XBlocks, and for your own learning.
While covering some of the same topics, this part of the tutorial is included as a later reference for using the XBlock SDK.