Gangnam is the name of a suburb of Seoul that literally translates to 'South of the river' as this is where it is located. 강(gang) = river, 남(nam) = south. 오빤(Oppan) is like a way of saying 'honey' or 'darling'

Oppa means A guy who is older than a girl. In Korea, For girls, If there is someone who is older than her, She calls him 'Oppa'. It can be her older brother or her boyfriend or even any older guy whom she knows. 'Gang-Nam' is a name of specific area of Seoul, which is known as where 'rich people' live. Apparently, It is not suburb. It is sooo inside Seoul. Therefore, In the lyrics, 'Oppa' indicates 'Psy' himself who sang this song. I would say it is that 'I have some style which is like some people who are from GangNam, which means that his fassion is kinda luxury, his car or home is fancy or something like that.'

Gangnam is a particular district (or suburb) in Seoul, which is known for it's expensive real estate. I'm pretty sure PSY explained it as "the Hollywood of Korea". 'Gangnam Style' literally translates to 'from the style of the Gangnam area'. (Making what PSY said on Ellen make more sense, "Dress classy and dance cheesy.") So the lyrics "Oppan Gangnam Seutail" mean "I am from the Gangnam Style" Talk To Me In Korean do a very in-depth explanation, if you're interested check it out: (http://www.talktomeinkorean.com/lessons/kpop-psy-4/)