Software is a set of instructions (commands that tell a computer what to do) that enable a computer to perform specific tasks or functions. It includes programs (specific sets of instructions) and data that are used by the computer. For example, web browsers, word processors, and video games are all examples of software.
Very Simple Definition:
Software is what makes computers work and do different things. It includes things like web browsers (to browse the internet), word processors (to write documents), and video games (to play games).