Like WeChat and WhatsApp, LINE is especially popular overseas, where many carriers don't offer unlimited texting.
The app has one interesting source of revenue: stickers. LINE has over 5,000 stickers and emoticons in its own app store for customers to send to friends. These icons are so popular LINE was able to use them to raise over $500,000 for hurricane relief in the Philippines this year.
Line, which is based in Tokyo, is valued at about $11 billion and could go public next year, according to the Wall Street Journal. It launched a little over two years ago and now has 300 million users. LINE is available for iPhone, Android, Blackberry, Windows, and Nokia.