There are typically three main categories of Hebrew: modern, ancient, and the Yiddish dialect (which is actually derived from High German and mixed with Hebrew, originating in Central Europe with the Ashkenazi Jewish community). Most online Hebrew courses focus on the modern language as used in Israel and by speakers in other parts of the world. However, if you're interested in Hebrew specifically for understanding ancient scripture (like the Bible) or for communicating with Hasidic and Haredi Jews in Yiddish, it might be worth it to look for lessons that focus on those purposes.