OCG

This is the official abbreviation for Duel Monsters in Asia. It's also known as the Yu-Gi-Oh! OCG.

Although it is the official name, the abbreviations "Yu-Gi-Oh" 「遊戯王」and "Yu-Gi-Oh Cards"「遊戯王カード」are more commonly used in Japan.. This abbreviation is often used to distinguish the cards from those appearing in manga, anime, and games that have different rules and specifications. Similarly, it is used to distinguish between the YU-GI-OH! TRADING CARD GAME (TCG) and the Japanese version. Other products in regions where KONAMI has consistently marketed them are officially called "YU-GI-OH Official Card Game (OCG)". Since September 1, 2013, a different list of Forbidden Limited cards have been applied in the TCG, but in the regions where the OCG is sold, the same list as Japan's Forbidden/Limited List is applied.

The OCG has jurisdiction over multiple countries in Asia. 

Japan - The original location and home of the game. 

South Korea - As the Korean OCG is the same as the Japanese one, the specifications are also the same.  Similarly, the TCG exclusive cards aren't included, but only the illustrations are modified to outside of Japan's specifications. It's released earlier than the other foreign language versions, often between the release of the Japanese version and the TCG version. Since the cards are produced in South Korea, the price is very low, and they're often sold in large quantities as PREMIUM PACKs (different from the Japanese version of the same name), making it easy to obtain cards that are rare in other languages.

Traditional Chinese - These cards are sold in Taiwan and Hong Kong, and are written in Traditional Chinese characters (the Chinese characters used in Taiwan and Hong Kong). It was released late, starting with Deck Starter Deck on January 29, 2014, so the card pool isn't nearly as complete as the Korean OCG.

Other countries - The OCG is also available in Malaysia, the Phillipines, Singapore and Thailand. But the text isn't translated, and the cards are exactly the same as the Japanese version. That means it's required to look up the cards and their effects on the Internet and memorizing it. Also, the price is the same as in the Japanese version because the cards are imported from Japan, meaning that they're more expensive than they normally would be. Because of this, pirated cards in their native tongues have been made and have spread through these countries with much cheaper prices. 

In the past, versions of the Japanese cards known as Asian-English cards were released in these countries starting with Legend of Blue-Eyes White Dragon on August 8, 2002. However, it was discontinued after Raging Battle released on August 6, 2009. The reason probably was poor sales, but I don't have the access to that information. Asian-English cards would see printing as prize, participation and as an attendance card until the 2015 World Championship.