In the simplest terms, it means that AI performance is less variable. A computer that can give you a good match on a good day will beat you on the days you're

In the simplest terms, it means that AI performance is less variable. A computer that can give you a good match on a good day will beat you on the days you're tired, distracted, or ill. And the computer won't have bad days. Conversely, if you're a bit better than the computer and manage to find a few of its weaknesses, you can exploit them again and again and it will never learn how to stop you (in any AI I've played against).