This document discusses Salesforce DX (sfdx), a new way to develop and manage Salesforce apps across their entire lifecycle. It outlines the goals of introducing sfdx which include discovering the new developer experience and taking a walkthrough of a simple use case. The document then explains what sfdx is, why it was created by solving issues with developer sandboxes, and how it can be used with tools like the CLI and commands like force:source:push. Finally, it provides an overview of how a sample use case would work, from retrieving and converting metadata to querying data and pushing/pulling from a repository.