A address bus is a communication pathway within a computer system that carries memory addresses from the central processing unit (CPU) to other components, such as main memory (RAM) and input/output (I/O) devices. It specifies the location in memory or the I/O space that the CPU intends to read from or write to.
The width of the address bus, measured in bits (for example, 16-bit, 32-bit, or 64-bit), determines how many unique memory locations can be addressed by the system. A wider address bus allows a larger address space to be accessed, increasing the maximum amount of memory and I/O locations the processor can reference and supporting systems with greater memory capacity and complexity.