Small point of correction: they are a race. They used to all share a common religion, but only a small fraction of Jews still practice their religion. Probably the only group of people on earth that are a race, and as a race followed a common religion. They were spread throughout the world by two disasterous events: the destruction of Jerusalem by Babylon a very long time ago (300 or 400 BC ???) and the re-destruction of Jerusalem in the year 70 by Rome. It is estimated that over one million Jews were killed by the Roman sack of Judea, and the rest fled for their lives throughout Europe, the Middle-East and Africa. There are some converts to Judism (the religion) but it's rare. They don't care much for outsiders.
But don't take my word for it, I've only been studying the Jews and their religion for the past twenty years...