LCD displays are commonly supplied as a module with a built-in driver circuitry usually mounted on a PCB at the rear of the module. While this strengthen the module mechanically, it has some drawbacks such as it increases the thickness of the display module and raises the manufacturing cost.
NXP semiconductors describes the Chip-On-Glass technology (COG) in this white-paper, whereby the integrated circuit driving the display mounts directly on the display glass, thus reducing the system cost. COG is a very reliable and well established technology, and offers very thin profile LCD display modules at lower cost.
For more detail: Chip-On-Glass (COG) technology for LCD displays
