Wikipedia
KakaoTalk (Korean: 카카오톡), or sometimes KaTalk, is a free mobile instant messaging application for smartphones with free text and free call features. It was launched on March 18, 2010 and is currently available on iOS, Android, Bada OS, BlackBerry, Windows Phone, Nokia Asha and Personal Computer. KakaoTalk currently has 170 million users and is available in 15 languages. The app is also used by 93% of smartphone owners in South Korea.
In addition to free calls and messages, KakaoTalk users can share diverse content and information including photos, videos, voice messages, location, URL links as well as contact information. Both one-on-one and group chats are available over Wifi, 3G or LTE and there are no limits to the number of friends who can join in on a group chat.
KakaoTalk automatically synchronizes the user’s contact list on their smartphones with the contact list on KakaoTalk to find friends who are on the service. Users can also search friends by KakaoTalk ID without having to know each other's phone number. The KakaoTalk service also allows its users to export their messages and save them for future reference.
KakaoTalk began as a messenger service, but has transformed itself into a platform for the distribution of various third party content and apps, including hundreds of games, which users can download and play their friends through the messaging platform.
Through the "Plus Friend" feature on KakaoTalk, users can follow brands, media and celebrities to receive exclusive messages, coupons and other real-time information through KakaoTalk chatrooms. Users can also purchase real-life goods through the messenger's "Gifting" platform, such as Starbucks coffee or jewelry.