An emulator is a software or hardware tool that mimics the operations of one system on another. This allows one computer system (the host) to run programs or execute commands designed for a different system (the guest). Emulators can simulate various types of hardware, including gaming consoles, operating systems, mobile devices, and more.
Articles by others on the same topic
One of the things Ciro Santilli really likes, see: Linux Kernel Module Cheat.