Anything superficial has to do with the surface of something. If you're judging a book by its cover, you're being superficial. People who worry too much about their clothes and hair may also be considered superficial.
The word superficial has to do with appearances and the surface. If a car is in an accident, but it only has a few scratches, you could say it has superficial damage, because the important parts are OK. If you just glance at a movie for a second, your opinion will be more superficial than the opinion of someone who watched the whole film closely. Superficial can have a negative flavor; calling someone superficial is saying that they are shallow and care too little about meaningful things.