I would encourage you not to try to understand everything referencing only the comm simulator.
This would be a good time to get some practical experience flying in and around the Class B by taking lessons. If you are flying out of MDW you will get plenty of radio work. Also, you will have an instructor right there who can help you understand anything that comes up, including the interactions between the Class B controller and other aircraft that aren't directed to you.
Also, remember Aviate Navigate Communicate. The radio comes after.
If I am near a busy airport I will take all the flight following I can get. It helps you, but it also helps the controller because they know who you are, where you are going, and can talk you around other traffic if need be, instead of having "unidentified traffic" at someone's ten o clock.