There is no Jewish central authority, and the modern movements are best understood as different answers to emancipation.
Orthodox Judaism holds halakhah to be divinely given and binding, and divides internally between Haredi communities, which limit engagement with secular society, and Modern Orthodoxy, which does not. Conservative Judaism, known as Masorti outside North America, treats the law as binding but historically developing and open to rabbinic amendment. Reform Judaism, which began in nineteenth-century Germany, treats the ethical content of the tradition as its enduring core and individual conscience as the arbiter of ritual observance. Reconstructionist and other smaller streams sit alongside them, and a large share of Jews affiliate with none of these while still identifying as Jewish.
The Holocaust ended the demographic and cultural centre the religion had built in Eastern Europe, killing roughly six million Jews and destroying communities that had existed for centuries. The population has not returned to its pre-war level.
Estimates of the world Jewish population cluster around fifteen to sixteen million, but figures vary considerably with definition: a core count of those identifying as Jewish and as nothing else yields a lower number than one including partial ancestry. Israel and the United States hold the large majority between them, with the next largest communities in France, Canada, the United Kingdom, Argentina and Russia. Hebrew is the liturgical language everywhere and, revived as a spoken tongue in the twentieth century, a vernacular in Israel. Yiddish and Ladino, the everyday languages of the Ashkenazi and Sephardi worlds, survive mainly in Haredi communities and in scholarship.