The meaning if you watch the movie is that this was they song that Christine and Raoul declare their love for each other and yes the phantom was Christines teacher but Christine is scared to death of him and wants to go on with her life. She fell inlove with Raoul and if you actually watch the movie Raoul and Christine are engaged to each other in the next scene and the phantom wants what he can not have. Christine loves Raoul and it is a really good song.