DOSBox is an open-source emulator that allows users to run software designed for the DOS operating system on modern computers. It creates a virtual environment that mimics the old hardware and software, enabling users to play classic games and use applications that may not be compatible with current operating systems. The emulator is particularly popular among retro gaming enthusiasts, as it supports a wide range of MS-DOS games and applications. With features like customizable settings and support for various file formats, DOSBox makes it easy to relive the nostalgia of older software on contemporary devices.