TYPO3 Neos is an open source content management system built on TYPO3 Flow. It uses a component-based architecture and supports features like Model-View-Controller, dependency injection, internationalization and localization. Websites can be built with Neos by creating node types and content elements, and configuring them using TypoScript and EEL expressions. The Neos command line interface allows managing domains, sites, workspaces and more.