What does the term 'bus' refer to in computer architecture?

In computer architecture, the term 'bus' specifically refers to the pathways that facilitate the transfer of data and power among various components on the motherboard. These pathways are crucial for communication between the CPU, memory, and peripheral devices. A bus system consists of multiple lines that can transmit signals, categorized into data buses, address buses, and control buses, each serving a distinct purpose in the coordination of the computer's operations.

The other options do not accurately describe what a 'bus' refers to in this context. While the physical casing of a computer is an important part of its overall design, it does not pertain to the internal workings and communication methods. Similarly, while connectivity of external devices is vital for a computer's functionality, it involves separate interfaces and protocols rather than the internal data pathways defined by a bus. Lastly, onboard storage capacity refers to the amount of data a system can hold but is not related to the bus concept, which is more about how components interact rather than the storage itself.