Mafia 83. Doctor Who: Aliens in London

This is the first time I've come across a topic of this kind. I really enjoy the classic game of Mafia (where you have the mafia, the cop, the medic, the... uh, typical European, and the townspeople), but here (no offense), it all seems very complicated and unclear. While reading about one "character," I forget about the previous ones. It looks interesting, but I'm afraid I won't be able to understand these character descriptions, the many abbreviations used in the descriptions, etc. However, if someone could explain the essence of the roles and what they do in a simple and detailed way, I would be grateful.