I’ve been writing glue code for ages. Basically, someone provides an API for a service. Could be the IBM PC with calls to the ROM BIOS to read files, or the Apple II hardware screen memory (invented by the clever Steve Wozniak), or the Apple Events supported by various Mac apps in the 90s, or the XML-RPC interfaces for web apps, or the REST interfaces of GitHub and Slack or thousands of other services. They give you an API, and then after you see what it can do, and if you want to use it in your app, you write some glue, so all your calls flow through code you control, so if you learn something about their API, you only have to support it in one place. It’s especially important for the few services that reserve the right to break their developers. Apple used to do this all the