A system software is a program that controls the entire computer i.e. Input, processing, output and backing storage needs for example Windows XP, Vista, etc. The system software is the base upon which the application software operates. Application software is a software that can be used for variety of tasks such as word processing (Microsoft Word), spreadsheets and databases.
Application Software is a program that did not come with your computer. Say for example if you downloaded Google Earth, that would be application Software. System software is a program that came with your computer. Say if you have a Windows computer, Windows Media player is an example of System software.