In a lottery, or a raffle, numbers are usually selected from a pool of possible values in such a way that once a number has been chosen, it is no longer possible for it to be picked again. For example the balls in a lotto machine are removed one at at time, and there is no way for the same number to be picked twice. Similarly in a raffle, winning tickets are drawn and then discarded so that the same ticket cannot win twice.
See here for mathematical information on lottery probabilities.
You can use the tool below to generate this kind of selection, specifying the range of numbers to choose from and how many different values you wish to choose.
These numbers could help you fill in a lottery ticket - or you can choose from one of the popular lotteries listed here: