What is Salesforce Dx in Salesforce?

Salesforce Developer Experience (DX) is a new way to manage and develop apps on the Lightning Platform across their entire life cycle. It brings together the best of the Lightning Platform to enable source-driven development, team collaboration with governance, and new levels of agility for custom app development on Salesforce.
Highlights of Salesforce DX include:

1. Your tools, your way. With Salesforce DX, you use the developer tools you already know.
2. The ability to apply best practices to software development. Source code and metadata exist outside of the org and provide more agility to develop Salesforce apps in a team environment. Instead of the org, your version control system is the source of truth.
3. A powerful command-line interface (CLI) removes the complexity of working with your Salesforce org for development, continuous integration, and delivery.
4. Flexible and configurable scratch orgs that you build for development and automated environments. This new type of org makes it easier to build your apps and packages.
5. You can use any IDE or text editor you want with the CLI and externalized source.
6. Salesforce Extensions for VS Code to accelerate app development. These tools provide features for working with scratch orgs, Apex, Lightning components, and Visualforce.