An emulator is a software program that enables one computer system to imitate the functions of another. This allows users to run applications, games, or operating systems designed for different hardware or platforms. Emulators are commonly used to play classic video games, test software across multiple environments, or preserve older technology by replicating its behavior on modern devices. They are essential tools in cybersecurity, software development, and digital preservation, as they help ensure compatibility and security when accessing legacy systems or files.