That means any iPadOS or iOS game that has been optimized for a controller will now play nice with your keyboard. Now, game controller buttons are mapped directly to keys on your keyboard and (optionally) your mouse. Apple has been steadily adding more capabilities to this feature, but the latest MacOS 11.3 update brings with it one of the most welcome changes yet.
If you have a Mac with an M1 chip, you can run iPhone and iPad apps and games right on your Mac.