VirtualBox is a free and open-source virtualization software developed by Oracle. It allows users to run multiple operating systems on a single computer, enabling them to create and manage virtual machines. This is useful for testing software, running applications that require different operating systems, or isolating environments for development. With VirtualBox, users can easily switch between different operating systems, such as Windows, Linux, or macOS, without needing to reboot their computer. The software supports various features like shared folders, snapshots, and network configurations, making it a versatile tool for both personal and professional use.