|Wikipedia has an article about
Yu-Gi-Oh! Trading Card Game.
Yu-Gi-Oh! Official Card Game is the version of the Yu-Gi-Oh! card game manufactured by Konami. It is played mainly in Japan and parts of Asia. The OCG is printed in Japanese and Korean. It has previously been printed in English (referred to as Asian-English) and has also had 3 different Chinese prints of cards, including two "Blue-Eyes White Dragons" and a "Dark Magician". Despite being part of the OCG, Asian-English cards have "Yu-Gi-Oh! Trading Card Game" printed on their backings, though with a different logo.
TCG cards are not legal in OCG tournaments. Due to Japanese, Asian-English and Korean cards having different backings, if a player chooses to use a mixture, they must use protective sleeves that cover the back of the cards.
OCG tournaments are divided into three classes: Expert, which has no age restriction, Regular: for secondary school students and Challenge, for primary school students.