People need sleep to properly function. If this is so, then how do people with insomnia function?

People are all different when it comes to this. I know several people who rarely if ever sleep and they seem to deal with it quite well. It is something to discuss with a Doctor and see if something can be done to help. Usually four or five hours is good enough for me and I find that the older people get, the less sleep they actually need. Different from person to person. Some have no problem at all with it and some really suffer.