Any programs which run on your computer come under the heading of software. Your favorite word processor, operating system or even your favorite game are all different types of software. There are many different types of software and you will learn more about them in the software section.
Without software your computer would not do anything. As most modern PC's are based on the Von Neumann architecture they rely on software to drive hardware. It is too expensive to get hardware to do anything other than run instructions laid out by software. This allows computers to be flexible and cheap to develop new programs for (compared to the cost of creating new circuit boards when you want a new program!)
