The article explains that Lacan's ideas about the formation of the "I" which I'm hoping means self (identity) elaborates with Freudian theory. The mirror stage simply focuses on developing a self image and distinguishing the "I" from other surrounding objects.
This article is short and to the point which makes it easier to understand. although Lacan is still tough to read. I would love to see a video presentation on the mirror stage. I'm sure that would give me and anyone else who struggled a better understanding and to see where exactly he is coming from.