Shaiel was right on. Some people chose to live among the Jews, and worship the same G-d, and follow the 7 Noahide laws. Not everyone would become Jewish...this if for many reason. For one, it isn't necessary to become Jewish to be considered a righteous person. Non Jews have 7 laws to follow, Jews have 613. With that said, when some does convert, they are not considered converts, and it is considered inappropriate to bring it up, or to ask questions about their old lives. Assuming someone completes an orthodox conversion they are considered Jewish in every way.