A data bus is a system within a computer or device, consisting of a connector or set of wires, that provides transportation for data. Different kinds of data buses have evolved along with personal computers and other pieces of hardware.
Techopedia explains Data Bus
In general, a data bus is broadly defined. The first standard for data bus was 32-bit, whereas newer data bus systems can handle much greater amounts of data. A data bus can transfer data to and from the memory of a computer, or into or out of the central processing unit (CPU) that acts as the device's "engine." A data bus can also transfer information between two computers.
The use of the term "data bus" in IT is somewhat similar to the use of the term "electric busbar" in electronics. The electronic busbar provides a means to transfer the current in somewhat the same way that the data bus provides a way to transfer data. In today’s complicated computing systems, data is often in transit, running through various parts of the computer's motherboard and peripheral structures. With new network designs, the data is also flowing between many different pieces of hardware and a broader cabled or virtual system. Data buses are fundamental tools for helping facilitate all of the data transfer that allows so much on-demand data transmission in consumer and other systems.