How does a software differ from a hardware?

In the most simplistic terms, hardware is tangible, software is not. Things like monitors, keyboards, mice, printers, hard drives, etc. are all examples of hardware. They are actual physical devices that you can see and touch. Things like Microsoft Windows, Microsoft Office, internet Explorer, Mozilla Firefox, etc. are all examples of software. They are not physical in any way - they only exist logically, within CDs or hard drives. The only way you can actually really "see" the software is by running the application on your computer.