The SE designation on a car typically stands for "special edition." It can also stand for "sport edition" or a special trim package.
The SE trim package is usually one of the nicer accessory packages in an auto manufacturer's product line. The base model would have no letter designation. The next model above the base model would have the ES trim package. Then, the models with the SE package and SS, or super sport packages take the next to highest rank within most car brands. Finally, the luxury models, marked with LE are offered with plush interiors and some extra luxury features. Specific labels do, however, vary by brand and can easily be checked on each car manufacturer's website.