Software is a generall term for imformation which is recorded onto some kind of medium.

Your computer is hardware, but the majority of things on your compuer is software. Most of the software is in the form of programs. Windows XP is an example of software which is on a computer.

If you want to buy something which will perform a specific task on your computer, it will be sotware. You may require a word processing program or something which will edit photos or graphics for you, all of these programs are software.