Can you guys tell me what is that?
Suddenly that things appeared on my ipad, can you guys tell me what is that? Thank you
The icon indicates that your iPad is synchronising with "something". Yours is at least the fourth report that I have seen in recent days.
As for what the "something" is, you'll hopefully have some idea as to what your iPad is connect to, or the App(s) that you are running on the device. Is the iPad physically connected to a dock or external USB storage device?
Apple's documentation is often slow to catch-up with new features. Here is another status icon - that appears briefly when connecting some USB-C hubs - that Apple have yet to add to their documentation: