I see that some names have the word "Rav" in the name, names like Rav Yitzchak Meir Morgenstern and Rav Berg.
I don't know much about Judaism. I want to know what is the meaning of "Rav".
In this sort of context, it is a title roughly analogous to the term "Rabbi." Here is how Wiktionary defines "Rabbi":
rabbi (plural rabbis)
- A Jewish scholar or teacher of halacha (Jewish law), capable of making halachic decisions.
- A Jew who is or is qualified to be the leader of a Jewish congregation.
You can find this word in many other dictionaries as well. Here is Wikipedia's article of that title.