Wireless keyboards:

The clearest difference between a wireless keyboard and a normal one is that the previous uses infrared beams to transfer data to the computer as opposite to the latter, which uses a wire. As you type, a beam of data is sent from your keyboard to a receiver on the computer. The main advantage of this is that it eliminates one wire from the entangled web of wires from behind your desk. Many people also prefer to have a wireless mouse along with a wireless keyboard.

Ergonomic keyboard

The ergonomic keyboard has been designed to ease some of the stress caused by repetitive typing and make for more comfortable typing. Protracted usage of the keyboard can cause carpal tunnel repetitive stress damage The particularly designed, contoured ergonomic keyboards are helpful in such cases and even recommended by doctors.

Illuminated keyboards

Much like mobile phone keyboards, these keyboards are backlit so that the keys are more noticeable even in poorly lit conditions frequently, when working at night, you may like to work only with the light of the monitor to stop the glare of another light. An illuminate keyboard would be just the thing for you in such a condition. It is also great for multimedia appearance in boardrooms with dim lighting.
When purchasing an illuminated keyboard, look out for the choice of being able to turn off the illumination when not required and to adjust the level of brightness.