Yiddish is actually the language of the Jewish people who emigrated from Eastern Europe to the USA. While Hebrew is the spoken language in Israel and the official language used in all the Jewish prayer books.
Unlike most languages, which are spoken by the residents of a particular area or by members of a particular nationality, Yiddish - at the height of its usage - was spoken by millions of Jews of different nationalities all over the globe. The decimation of European Jewry during the Holocaust in the mid-twentieth century marked the end of Yiddish as a widely spoken language and of the unique culture the language generated. Today, select groups of ultra-Orthodox Jews continue to use Yiddish as their primary language.
To learn the most popular Yiddish phrases click on the link.