ARexx is the Amiga implementation of the REXX scripting language, developed by Mike Cowlishaw and ported to the Amiga by William S. Hawes. It serves as an inter-process communication system that allows users to write scripts automating tasks across multiple applications simultaneously. ARexx ports enabled programs like text editors, music sequencers, and graphics software to be controlled remotely, making it a powerful tool for automation and macro creation on the Amiga platform.