Computer software is a set of instructions that operate computers and execute tasks. There are two main types: system software and application software. System software controls a computer's internal functions through the operating system and provides a platform for applications. It includes operating systems, utility programs, device drivers, and language processors. Application software performs specific personal, educational, and business functions like Microsoft Office, Spotify, Google, and Facebook. The main difference between the two is that system software is general purpose, always running, and essential, while application software serves specific purposes and runs only when needed.