Daughter cards are derived from and connected to the main board (called a mother board). They are printed circuit boards (PCBs) that can be used to add functionality to a system. As an example, an add-in graphics card and a network card are both daughter cards. They contain additional components and connectors and are designed to fit into a specific socket on the motherboard.
OEM boards are circuit boards that are integrated into a consumer electronics device by the original equipment manufacturer. The manufacturer will design and build the board, then sell it to the OEM who will manufacture the entire device. These boards are generally designed to customer specifications and can be used in TV sets, game consoles, audio players, and more. OEM boards may include components such as video processors, memory chips, processors, and other components.