An example is the best way to describe it. My best friend is named Bob. Really - that's his name; I'm not making this up. His was the first name I used when trying the Assist function for the first time. I had already spent some time with my MessagePad 2000, entering names and such. So, I opened the notepad application, wrote "Call Bob" and tapped the Assist button. I didn't even have to select the phrase "Call Bob" first.
What happened next was exactly what you would expect to have happened. A slip popped up on the screen that had good ol' Bob's phone number on it, and a button labelled "Call". There was a menu that gave me choices for how to dial; I wasn't physically connected to the phone so I selected "Using Speaker" and pressed the call button. Then I placed the phone to the Newton's speaker and, sure enough, it dialed Bob's phone number for me. Bob didn't answer -- I guess he was out doing Bob-type things.
The Assist feature knows several different verbs, and can be extended to understand even more. The verbs it know about fresh outta-da-box are call, fax, find, mail, print, remember, reschedule and time. Those are what appears in a pick list, but the Newton knows several variations. For example, "call Bob", "dial Bob", "ring Bob" and "phone Bob" all do the same thing. I'm not about to list all of the synonyms for "Schedule" (meet, talk with, breakfast, lunch, brunch, dinner, anniversary, ...)
How about another example? Right now I don't have any applications running except for Backdrop+ (Standalone software: http://www.standalone.com). It has a feature that lets me enter a quick note. Not the notepad application per se, just a slip that let's me write a short note. Let's try "Lunch with Bob" and see what happens. I actually wrote "Lunch w/ Bob" and the Newton got it right because I had defined "w/" to be shorthand for "with".
The Newton is now displaying a slip that shows a meeting from 12:00 to 1:00. The list of invitees properly includes Bob's full name (I only have one Bob in my list of names). I can now just press the "Schedule" button or adjust the time or other facts about the meeting. I happened to do this at 9:30 this morning. Had I done this between 12:00 and 1:00 the meeting would have been scheduled in the next half hour. After 1:00 and it would have been scheduled for tomorrow (assuming I already ate lunch today). Isn't that clever?
What's so marvelous about this is the integration of Assist with both the built-in Newton software as well as third-party applications like Backdrop+. I wrote the note using Backdrop+, then tapped Assist. The Newton looked up "Bob" in the built-in names application then requested the dates application to create a new meeting. Backdrop+, names, dates, Assist, all working together.
Here's a fun Assist trick: Daydreaming about a vacation and want to know the time in some other part of the world? Just write "Time in Melbourne and tap Assist. You get the little time application showing the current time in Melbourne, Australia (1:46 am Fri 5/23 as I write this).
The beauty of this feature is that it works so simply and intuitively. I really didn't have to learn how to use Assist other than to know what button to tap. I can just write a note using plain english and Assist will try to figure out what I mean. I don't have to use the notepad, BTW, Assist can pop up a slip to let me enter a phrase or pick a verb from a list. Since I use the notepad frequently on my Newton, writing the phrase and tapping Assist is easier for me than doing it the other way around.
In and of itself, Intelligent Assist is not a "Killer App" for the Newton. It's just yet another feature that makes Newton incredibly simple and easy to use. There when you need it, out of the way if you don't. Including it as part of the base OS was a very good thing indeed.