A trackball simply is a pointing device with a ball in a sort of socket which is containing sensors that will detect the rotation of the actual ball. An optical trackball on the other hand is a bit different.
Optical trackballs usually use very tough state Optical Navigation Technology in place of the traditional mechanical assembly of conventional trackballs. The only moving part in the entire assembly is actually the ball, whose movement is sensed directly without the need for shafts, separate encoders.
Industrial Optical trackball are more and more used along with industrial LCD displays and Industrial Computers. As they are being used in a tough environment, they too need to be tough and able to resist to everything from a continuous outdoor use, to high temperatures and dust. This is the reason why industrial optical trackball are usually waterproof and very often nearly maintenance free.
Industrial optical trackball can be used in public environments as well. Being waterproof and even vandal proof, they can withstand intensive use outdoor. You can find those trackballs in information kiosks for example.
They go perfectly well with industrial keyboards when a mouse can not be used. You can even get keyboards with an incorporated trackball in it. Those keyboards will obviously have to be as tough as the trackballs. But with so many different kinds of industrial keyboards available for industrial use, you will have plenty to choose from. Some people may find better to use a handheld keyboard that would enable all major functions of a large keyboard in a small device, whereas other will need a more classic keyboard. They are usually waterproof, and a protected and reinforced to be able to cope with dust, and any other harsh environment.
You can even find rugged stainless steel keywords now. They are very suitable for a number of harsh and public access environments like information kiosks and public access devices. Being protected by stainless steel, they offer a better protection against water and any other element involved in an everyday use in an outdoor environment.
In the end, you have to be very careful when choosing a device when it is to use it in an industrial environment or for public use. Industrial display monitors like industrial LCD displays, industrial keyboards and optical trackballs are among the main parts you will need to be very tough to resist to a harsh environment.