Touch screens allow you to interact with a computer in new and interesting ways. These screens used to be relatively expensive, but as they are coming down in cost, you may be considering why they would be a good purchase.

Interaction Simplicity

A modern keyboard has more than 100 buttons on it, and learning to type properly can take weeks or months. Using a touch screen allows you to bypass this obstacle for basic tasks, such as navigating a DVD menu or making visual shopping selections.

Keeping the Device Clean

Although more expensive than a keyboard, opting for a touch screen makes for an easier-to-clean input device. Make sure that you have cleaning tools that are specifically designed for monitor screens, or else you may scratch them.

Novel Interaction

Multitouch screens allow you to use certain intuitive hand gestures for things such as zooming in on an image, rotating it and selecting specific areas. This is particularly handy for map navigation.

Security

If you have a touch screen set up in a public kiosk, you can avoid using a keyboard and therefore reduce the possibility of someone bypassing your protective mechanisms and using the computer for questionable purposes.

Practicality

Sometimes it's just not practical to attach a keyboard. You don't have enough room, or you can't afford to glance down at the input device. This is particularly the case with automobiles and their dashboard map navigation or media players.

Source:

How Touch and Multitouch Work

Touch Screens go Mainstream

Varieties of Touch Screen (With Video)