Seems like Duolingo should be careful teaching this phrase without context. In some countries, this can be considered a very rude way of asking the question. In Mexico, they would say "me explico?"if they were trying to ascertain whether someone understands something. Or they would give more context when using entender... like do you understand me when I speak Spanish? Using it alone could rub folks the wrong way.
DL's suggestion to me was "Do you get me?" Maybe that's closer to the sense of it.