Keyboard wireless feedback from computer
Most modern keyboards use a USB interface.  Likely they are using the HID protocol within the USB families of protocols. There is support for 2 way communications within the HID protocol.  Some keyboards may take advantage of this so that the computer can control keyboard indicator lights.  Some wireless keyboards use a Bluetooth interface.  Bluetooth, like USB, has a definition for the HID protocol. There are also vendors using proprietary protocols.  We can assume there is some 2 way communications as inferred by features such as battery level monitoring.