Nominee directors are used to conceal the identity of the beneficial owner and their use renders director information reported to the companies registry. For example if you open a Cyprus offshore company you will need to have a nominee director if you don't want to be registered as director in the company.
I don't remember if it is a must, but anyway most people use a nominee director for the offshore company registration.
Comon guys, you will need to read alot more about what you are considering to do, once of the most important things are, How do you go an structure your company. In another thread their was a discussion about to do business planning, I guess above is an answer to this thead too.