Short answers, pulled from the story.
Ashkenazi Jews trace their origins to Jewish communities that consolidated in the Rhineland (western Germany) and northern France during the 10th century, having migrated from centers in the Italian Peninsula and the Southern Levant. Genetic research indicates their deeper ancestry lies in ancient populations of the Middle East, with both paternal and maternal founding lineages pointing predominantly to a Near Eastern origin.
At their population peak around 1930, Ashkenazim were estimated to account for 92% of world Jewry. After the Holocaust, estimates place their current share at roughly 74% to 85% of the global Jewish population, depending on the methodology used. The estimated Ashkenazi population today is around 10-13 million out of approximately 15.8 million total Jews.
Historically Ashkenazi Jews spoke Yiddish, a Germanic language written in Hebrew letters and heavily influenced by Hebrew, Aramaic, and Slavic languages. Before the Holocaust, more than 11 million people worldwide spoke Yiddish. Following the Holocaust and the revival of Hebrew as a spoken language, Hebrew has replaced Yiddish for most Ashkenazi Jews, though Hasidic and Haredi communities continue to use Yiddish in daily life.
Of an estimated 8.8 million Jews living in Europe at the start of World War II, about 6 million, more than two-thirds, were systematically murdered in the Holocaust, the large majority of them Ashkenazi. Poland lost 3 million of its 3.3 million Jews (91%). The Holocaust also ended the dynamic development of Yiddish, as approximately 5 million of the Jewish victims were Yiddish speakers.
The Khazar hypothesis, proposed in the late 19th century, suggested that Ashkenazi Jews descended primarily from Turkic Khazar converts who migrated westward into Central Europe, rather than from Jews who migrated eastward from France and Germany. A 2013 study by 30 geneticists from 13 universities across nine countries found no genetic evidence supporting this hypothesis, concluding that Ashkenazi Jews derive their ancestry primarily from populations of the Middle East and Europe.
Ashkenazi Jews follow the German rite synagogue ritual, codified in Joseph Karo's Shulchan Aruch (1563) together with the notes of Moses Isserles. Distinctive customs include refraining from legumes and rice during Passover, naming newborns after deceased rather than living relatives, wearing wigs as a hair covering for married women, and pronouncing certain Hebrew letters differently from Sephardic Jews, notably the letter tav as an /s/ sound in specific contexts.