Computer software (or simply software) refers to one or more computer programs and data held in the storage of a computer for some purpose.
The term software was first used in this sense by John W. Tukey in 1957.
Computer software is so called in contrast to computer hardware, which is the physical substrate which stores and executes (or "runs") the software.
Computer science divides software into two big classes: system software and application software. All other subclasses belong to these two classes.
System software helps run the computer hardware and computer system. It includes operating systems, device drivers, programming tools, servers, windowing systems, utilities and more.
Application software (Apps) allows a user to accomplish one or more specific tasks. Typical applications include office suites, business software, educational software, databases and computer games. Most of application software has GUIs.
Further reading on Wikipedia:Software