AOL stands for "America OnLine", a leading commercial provider of email accounts and access to the internet. It merged with New York City based conglomerate Time Warner in 2001, and in the past few years, its business model has increasing shifted to an advertising-supported one, serving ads both on their own sites and to third-party sites via their Platform-A distribution system.
In 2009, Time Warner bought out Google's minority stake, and then AOL was spun off into a separate, publicly-traded company, initially owned by Time Warner's shareholders. In 2011, it acquired the liberal Huffington Post. In 2015 Verizon announced that it would acquire AOL for $50 per share, or approximately $4.4 billion.