A motherboard is the main printed circuit board (PCB) in a computer, serving as the backbone that connects all components. It houses the CPU, memory, and expansion slots, allowing communication between various hardware parts. The motherboard also provides power to these components and facilitates data transfer through buses and connectors. Different types of motherboards exist, such as ATX, MicroATX, and Mini-ITX, each designed for specific use cases and form factors. Choosing the right motherboard is crucial for system performance and compatibility, as it determines the types of processors and memory that can be used, as well as the number of expansion slots available for additional hardware.