It looked like a mere word processor, but—much like Emacs, especially org-mode—the Canon Cat was actually contextually aware of what the text meant, and allowed other operations to be performed on it as appropriate. For example, if you start typing numbers into tables, spreadsheet-like functionality became available, including the ability to perform mathematical operations over those numbers and have cells dynamically updated with the new values. Raskin called it a "work processor".

The Forth language was available for programming and extending the machine, via a cheatcode. You had to type in the phrase "enable the Forth language" and evaluate it with a special command or something—you know, one of those things to provide hackability for those who needed such while keeping it an office appliance for the vast majority of users. I don't know if there was an intent for a market or library of third-party software, but that doesn't seem to have arisen.