What is a computer system? 

According to WordNet, a computer system is defined as, "a system of one or more computers and associated software with common storage."

The above definition explicitly named two components: hardware and software, sharing a common storage, as what constitutes a computer system. There are many examples. We use a computer system in banking, retails, health, travels, education. Basically any tasks that involve storing and processing of bulk data would benefit by being computerized. A computer system may consist of a standalone computer (like your desktop PC or laptop), or agrid of networked computers. It may require a single software, or a multitude of software. A computer system may even appear in a different form than your conventional concept of one such as the one you can find inside your calculator!

Computer Hardware 

Basically, computer hardware covers the physical parts or components of a computer. This may include the monitor, mouse, keyboard, hard drive and so on. To put it simply, computer hardware are objects that can be touched.