Judaism is the religion of the Jewish people. It provides the basis for two other major world religions, Christianity and Islam. Its philosophy, rules, and values are derived from the Torah, supplemented by a long history of rabbinic interpretation and constantly-evolving traditions and culture.
There are many different varieties of Judaism. To some people, Judaism is a culture, replete with its own foods (bagels, kugel, falafel) vocabulary (including Yiddish, Hebrew, and Ladino words) and ethnic figures. To some, it's a religion, with distinct rituals and belief in the God of the Hebrew Bible.