What's the use for computers?

The problem of understanding (and design):

What do computers do? What can you do with computers? What can you not do with them?

What's the use for computers?internet security

They can be used to prepare French Fries. In rainy days they can be used as umbrellas. I also have seen computers being used as water containers (tanks)

What's the use for computers?network security

Games and information. And computers can only do what you tell them to do.

They can't cook, clean house or bathe for you. They can't go to work for you when you call in sick. They can't feed your dog or drive a car or perform brain surgery on your llama.
they perform calculations faster than a human. You cannot calculate big math equations without them Some of these calculations help in the fight against cancer and other diseases. Tracks economic conditions.
That's a very simple question with a complex answer.

Computers today are commodities, items needed to make our life more comfortable. We need them at work, at home, at school, we need them on a daily basis for a variety of reasons.

You ought to see them not as the PC/Mac units, but also at your computer's car, at your mobile phone, at the red/green light you see everyday which is controlled by a computer and for much more things.