VirtualBox
Virtualization software for x86_64 hardware
...It supports a wide variety of host platforms (Linux, Windows, macOS, Solaris, etc.) and guest OSes, enabling, for example, running Linux on a Windows PC, running Windows Server on a Linux host, or even legacy OSes in a controlled environment. This flexibility makes VirtualBox ideal for developers, testers, sysadmins, or hobbyists who need different OS environments, want to test software across systems, or need isolation for development, sandboxing, or security experiments. VirtualBox offers both a user-friendly GUI as well as a command-line interface and headless mode, making it useful for desktop usage as well as server or automated environments.