Gangnam is the central district of the southern half of Seoul. Though Jongno and Jung to the north may claim to be the center of Seoul, in many ways Gangnam is the true center of both Seoul and the entire country, "immortalized" and parodied by Psy's infamous song "Gangnam Style". Believe it or not, fifty years ago this entire area was rice paddies and pear farms. Everything you see here has been built since then, the construction mirroring South Korea's economic rise.
Gangnam in and of itself is large enough to split into two main districts, Apgujeongdong and Cheongdamdong to the north, and Gangnam/Tehranro/Samseongdong to the south.
Apgujeongdong and Cheongdamdong are both by the Han River, and earn the distinction of being perhaps the richest neighborhoods in all of Korea. Posh cafes, brand name handbags, Mercedes and Porches, ritzy department stores, and rows upon rows of luxury brand clothing stores characterize this neighborhood. Unsurprisingly, many of Korea's movie stars and singers make their home here, and are occasionally spotted enjoying some Patbingsu or sporting new sunglasses. There is also a sizable nightlife scene here, though it is relatively laid back compare to the chaos that is Hongdae/Sinchon. Most of it caters to upper-class Korean teenagers and young adults. Strangely enough, the apartment buildings here look no different from the rest of the city; if anything, the apartment buildings here are some of the oldest and shabbiest looking. This can be explained by the fact that the upper-class elite who reside here are fiercely opposed to new renovations and expansions, as they fear an influx of new residents will drive housing prices down and make the area unbearably crowded.
Tehranro, in stark contrast, is a long avenue with many glass skyscrapers running along both sides. Nicknamed "Tehranro Valley", after Silicon Valley, most of Korea's hi-tech companies are headquartered here, such as Naver and Samsung. The east end of Tehranro is Samseong Station, which has COEX and Bongeun Temple. Seolleung Station, in the center, has a park with some ancient royal tombs. The west end of Tehranro is Gangnam Station, the busiest subway station in the country. The station opens onto Gangnamro, a futuristic avenue that is bursting with modern skyscrapers, high-end shopping (though not quite as high-end as Apgujeongdong), cafes, bars, restaurants, huge television screens, neon advertisements, and thousands of pedestrians drinking it all in. Strangely overlooked by many tourists and the Seoul Government as a tourist attraction, Gangnamro truly epitomizes the modern, hi-tech country Korea has become in the past 60 years.
Apgujeong (압구정), widely known as "The Beverly Hills of Seoul" is the land of luxury, brand name goods. International brands like Chanel, Louis Vuitton, Dior, Gucci and Prada sit alongside Korean designer brands.
Near the Cheongdam Intersection lies the heart of the Korean shoe scene. Cutting edge shoe shops include Sue Comma Bonnie, Hyaang, Heels and Namuhana.
Apgujeong (압구정) is the upmarket area of Seoul. Walk around the streets and you'll see teenagers valet parking their new Benz or Audi, strutting their new designer threads, and looking generally, well, rich. That said, a lot of people who party here aren't necessarily rich and live far away. Apgujeong is rather subdued when it comes to nightlife though it has a few posh clubs and bars. Places where valet is unavailable are unlikely to be great hits traditionally. There are, however, a few small clubs in the area. Expect English to be more commonly spoken in this area, too, due many Koreans in the area having studied abroad or received a lot of private tutoring. This has also meant, however, a certain desensitization to foreigners, so don't expect people to stare or approach you as much as they would in other parts of Seoul. Consider Apgujeong a great place to hang out, not party. If you want to impress a date for example, this is a great place to go to. The backstreets of Apgujeong tend to sprout and lose new clubs seemingly at random throughout the year, so getting off the main drag from time to time can yield a new "hot club of the month."
Gangnam station (강남) is probably the No. 2 club area in Seoul. Also set up in a grid structure, clubs, bars, restaurants and other entertainment venues decorate this upmarket location. While not as upmarket as Apgujeong, it definitely is busy and lively. If Apgujeong is the place for rich kids to hang out and look cool, Gangnam is the place for those rich kids to party and look sexy. The station is a transit hub and a ton of buses run through the heart of the entertainment area, so finding your way there is extremely easy.
please note that there rare multiple, unaffiliated, Woodstock bars in Seoul - this entry is for the one on Yeoksam-dong side of Gangnam station.