A TV remote control uses a modulated infrared light beam, as do certain laptops, Palm device, and printers. Mainly, wireless means using radio transmission to communicate across almost any distance. Clever use of packet, time-slicing, compression, and cellular techniques are making better use of the radio spectrum, but the limits aren't going away. Most wireless transmission is between mobile unit and base station. But there's a lot of non-mobile wireless.
Some examples are TV station to home, satellite to home or business, and long-distance telephone.
In some areas, fixed wireless serves homes that can't get pay TV or fast Internet connections via cable. The new excitement is about wireless mobile networking of digital data devices. The various wireless wide area network schemes primarily use existing telephone networks, including the analog cell phone network, the several PCS digital networks, the GSM network in Europe, and others. They're all mutually incompatible, expensive, and compared to a wired network, slow. It's going to get worse as demand for wireless exceeds the political, legal, financial, physical, and time hurdles that wide area network builders face.