The  network of wires or electronic pathways is called the 'Bus'.

• A system bus is a single computer bus that connects the major components of a computer system.
•  It combines the functions of a data bus to carry information, an address bus to determine where it should be sent, and a control bus to determine its operation.
• The technique was developed to reduce costs and improve modularity. 

The three different types of buses are :

• Address Bus
• Data Bus
• Control Bus

Address Bus : 

• It is a group of wires or lines that are used to transfer the addresses of Memory or I/O devices.
•  It is unidirectional.  
• The width of the address bus corresponds to the maximum addressing capacity of the bus, or the largest address within memory that the bus can work with.
• The addresses are transferred in binary format, with each line of the address bus carrying a single binary digit.
• Therefore the maximum address capacity is equal to two to the power of the number of lines present (2^lines).

Data Bus

•  It is used to transfer data within Microprocessor and Memory/Input or Output devices.
•  It is bidirectional as Microprocessor requires to send or receive data.
•  Each wire is used for the transfer of signals corresponding to a single bit of binary data.
• As such, a greater width allows greater amounts of data to be transferred at the same time.

Control Bus

•  Microprocessor uses control bus to process data, i.e. what to do with the selected memory location.
•  Some control signals are Read, Write and Opcode fetch etc.
• Various operations are performed by microprocessor with the help of control bus.
•  This is a dedicated bus, because all timing signals are generated according to control signal.