These three dots connect to Apple's smartkeyboard.
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It is a magnetic connection technology that does not require the use of Bluetooth and cables. It can also be adapted to some third-party keyboards and charging stands. There are only a few ways to use it, and Apple hasn't developed any new apps to work with it. So the main way to use is to connect the keyboard, and this keyboard than the previous generation has improved a lot, feel better, but still unsatisfactory.
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Extended information:
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In terms of hardware, the iPad2019 isn't much of an improvement, but the larger screen size allows it to use the official SmartKeyboard. On the software side, since iPadPro is ahead of iPadados, it can do even more. The content is big enough to consume, light enough to generate targeted content, and cheap enough to make it the friendliest iPad ever
The three points to the left of the ipad are the contact points for the Smart Connector's wireless Keyboard. The so-called Smart Connector is a magnetic interface technology that Apple created specifically for the iPad Pro and has not yet spread to other products. Through this interface, the iPad Pro can generate two-way data and power transfers with connected accessories.