Lucky numbers change from person to person, and are any digits of personal significance or value. For many people, lucky numbers mark the birthday of a child or significant other, an anniversary, a jersey number they wear/wore or any other numbers relating to a sentimental possession or event.
Most lottery players' picks are made using "lucky" numbers. However, choosing the same numbers each time has no bearing on the likelihood a given number is selected and does not statistically improve chances of striking it rich. Most people use the same numbers out of superstition, for peace of mind, or simply to avoid the regret of not picking them in the event they are selected.