Question about Microsoft Surface Pro Flex Keyboard

Yes, it even needs to be charged.

Yes, this is the standard configuration.
It has two magnetic elements on the keyboard that fit into two indentations on the edge of the Surface and are held there magnetically.
This allows you to use the keyboard as a cover for the screen or - when opened - as a laptop keyboard.

Yes, the keyboard can be plugged into the Surface like the other Surface keyboards and is the lid in front of the screen when closed.