While gaming, the scroll wheel may allow you to switch weapons or perform some other task by rolling the wheel. Cordless mice do exist and prove very handy to many people. Some mice use infrared technology. This would require your mouse to be relatively close to your computer as a clear line of sight will always be required. Some mice also use RF technology, which does not require a clear line of sight between your mouse and your computer.
Cordless mice work great at presentations or simply at home.
Some of them can function while up to six feet away. Chances are you already own a mouse. You shouldn't have much trouble replacing it, if need be. Mice and other pointing devices normally connect to a PS2 or Serial port on PCs and some higher-end models have a USB connection option. For desktop computers pointing devices are very different for PCs and Macintosh computers.