Mouse, the classic input device. Modern ones features laser tracking, and thumb wheel.
Apple Magic Mouse. The entire surface is smooth. No buttons. No scroll wheel. It works by touch sensitivity, like a touch pad. And you can use “gestures”. For example, to left click, tab on the left side with one finger. To scroll, move your finger on the surface up or down. To zoom, touch the surface with two fingers and widen your fingers.
Is this good mouse? No. If you want to impress your friends, yeah. If you want it for industrial use, ⁖ heavy gaming, long hours in image-editing or editing in 3D Modeling Software, it suck badly. Tire your fingers, rub your skins off.
The Magic Trackpad is just a large trackpad. That's all.
Rub your fingers on metal. Rub rub. Rub rub.
Every few years, Apple comes out with shiny and novel toys. Actually i don't recommend them. If you are a casual computer user, yeah Apple's input devices look great and work well. If you are in any way using the computer professionally, such as serious gaming, PhotoShop or visual artist, creating 3D Models, or programing (heavy Emacs or keyboard Macros use), Apple's creative input devices are usually less efficient and less ergonomic than the humble homely standard ones.
See also: Apple Keyboard Reviews.
Now, if you do a lot image editing or drawing, you need a pen tablet, absolutely. This is something i can recommend.
See: Best Trackballs Comparison.
See: What's Jog-Wheel? What's Shuttle-Wheel?.
Many gaming and 3D modeling software can use a specially designed input device. ⁖ Second Life, Google Earth Mouse Navigation and Keys, Flight Simulator, and other 3D Modeling Software.
See: SpaceNavigator, Math Models of 3D Inputs Control.