A computer system consists of two parts - hardware and software. The first part, computer hardware, refers to all the visible components of the computer system: keyboard, monitor, hard disc, printer, scanner, processing unit, memory, electrical connections, etc. It does all of the physical work a computer is known for. The second part is a set of simple and step-by-step sequence of instructions that tell the hardware what to do and how to do it.
This organized set of instructions written in a defined order and to accomplish a specific task is called computer software or computer program. Hence, a computer software provides intelligence to the hardware, which otherwise is just a collection of circuits and pieces of plastic and metal.