A lot depends on the focus of the course.
When you get up to MA there are a whole host of things to look at.
Describing photographs.
Interpreting photographs.
Evaluating photographs.
You can look at types of photographs, context, ethics, aesthetics.
And others.
You can look at all of these from different viewpoints, too.
Realism, conventionalism, modernism, post-modernism, Marxism, feminism...
What you look at and the stance you look at it from depends upon the course you do and the preferences of the lecturers. Not to mention what is trendy*.
It can all be very complicated - and the language can be very difficult too.
The best place to start is by reading Susan Sontag's 'On Photography' and Roland Barthes' 'Camera Lucida' and take it from there.
* Currently it's the Structuralists. I prefer the Deconstructionist approach, myself.