An emulator is a software or hardware tool that allows one computer system to mimic the functions of another. This enables users to run applications or games designed for a different platform, such as a video game console or an older operating system, on their current device. Emulators are commonly used for testing software, playing retro games, or running applications that are not available on a specific system. Emulators work by replicating the original system's architecture, including its CPU, memory, and input/output processes. Popular examples include Dolphin for Nintendo GameCube and Wii games, and BlueStacks for running Android apps on Windows or Mac computers.