The short version
A CarPlay AI box (also called an Android AI box) is a small device that plugs into the USB port your car uses for wired Apple CarPlay or Android Auto. Inside, it runs Android, so your dashboard screen gains an app launcher and, on most models, wireless CarPlay.
What you get
Wireless CarPlay or Android Auto without a cable, plus apps like YouTube and Netflix for passengers when parked. Some models add a 4G SIM slot so the box has its own data.
What you do not get
It will not add CarPlay to a car that has none, and it does not make your screen touch-enabled if it is not already. Most boxes need factory wired CarPlay or Android Auto first.
Is it worth it?
For a car with wired CarPlay, it is a cheap upgrade compared with a new head unit. Start with the wireless CarPlay best sellers and check compatibility first.