If you’ve met three Jews in your life and have talked with them about Judaism, you’ve probably gotten about SIX different viewpoints! Jews are notorious for being independent and have different perspectives on practically everything, not only their religion.
There are some Jews who identify with their Judaism only in a cultural way. Some of them may even be atheist. They still, however, consider themselves Jewish. The upshot is that one may be Jewish and not participate in any of the holidays or customs, and not even believe in G-d. It sounds contradictory, but it is possible.
The differences between Orthodox, Conservative, and Reform Jews (I would also add Reconstructionist Jews) are many, both in the details of religious observance and in the general philosophy of what Judaism is all about. With regard to the details of religious observance according to the strict practice of the Law, Orthodox Jews are the most observant, Conservative less so, and Reform least so. It should be kept in mind too that Orthodox Judaism is an umbrella term that incorporates a lot of different types of Orthodoxy: Chasidic, Traditional, Modern. And within Chasidic Orthodox, there are different sects as well. Moreover, Reform Jews are not all alike in their practices, and neither are Reconstructionist Jews. There is even more complication in that there are small pockets of Jews who do not neatly fit into the larger movements: for example, Karaite Jews (they are sola Scriptura, following ONLY the Written Law of the Torah but NOT the Oral Law of the Mishna and Talmud) and Nazarene Jews, who believe in the Messiahship of Jesus but not His divinity. They do not consider themselves in the same group as Messianic Jews, however. Finally, customs among Jews, regardless of degree of orthodoxy, vary according to the region and country in which they live. In broad terms, they can be divided into Ashkenazi and Sephardi, but even this division is a simplification.
With respect to the afterlife, most modern Jews, in accord with the Pharisaic tradition, do believe there is one although, since the specifics are not detailed in the Law, there is permissible variation regarding what it may encompass. The bodily resurrection is one of the tenets of Jewish faith based on the principles formulated by Maimonides. Not a tenet but nonetheless a belief held by some, generally Orthodox, Jews (but by no means all Orthodox Jews) is that of reincarnation. It is not the kind found in Hinduism, however, but rather is generally for the purpose of accomplishing an important, righteous task which had not been completed in the present lifetime. Still, some Jews do NOT believe in an afterlife nor a personal Messiah. This group would include mainly Reform and Reconstructionist Jews, but again not all of them.