UDC
(Under Display Camera)
A camera that is hidden under the surface of a an active display area. Typically, this is a front-facing camera hidden under the main display of a phone or tablet.
The purpose of an under-display camera is to enable a display that covers most of the front surface of the device without a "notch" or "hole punch" cut-out for the camera.
This technology is enabled by special display technology — usually localized to just the area over the camera — with pixels that are smaller, enabling that area of the display to be mostly transparent to the camera.
See: Pixel
Image processing software may also play a role in compensating for the display's effects on the image from the camera sensor.
An under-display camera is generally only possible with OLED display technology.
See: OLED