Possibly the difference between "Computer Science" and "Computer Studies"?
What I mean is, "Things that a CS major probably should have been exposed to in his or her first year of college."
Look at it like any other subject: you spend a lot of time analysing and understanding existing work before you make new work. Why would it be different for computer science?
The introductory course syllabus is at http://www.cl.cam.ac.uk/teaching/1011/CST/node11.html if you're interested.