There's several Jewish ethnicities. The largest are Ashkenazi (Euro; 90% of American Jewry) and Mizrahi (MENA; majority of Israeli Jewry). Judaism is a religion

There's several Jewish ethnicities. The largest are Ashkenazi (Euro; 90% of American Jewry) and Mizrahi (MENA; majority of Israeli Jewry). Judaism is a religion, so people who aren't ethnically Jewish can convert, but it's also an ethnic identity, so Jews who drop Judaism or convert to another religion (like nearly all famous 19th century Ashkenazim) are still Jewish.