Vagrant is a tool that allows users to create and configure virtual development environments. It uses a file called a Vagrantfile to define virtual machines that can be used for development and testing. The Vagrantfile contains instructions for provisioning the virtual machines, including installing software, configuring settings, and more. Chef is one tool that can be used for provisioning - it allows defining recipes for installing packages, configuring servers, and deploying applications like TYPO3 Neos. The document provides an example of using Vagrant and Chef together to automatically install and configure a TYPO3 Neos CMS development environment in a virtual machine.