Google AdWords is an online advertising service developed by Google, where advertisers pay to display brief advertising copy, product listings, and video content within the Google ad network to web users. Google AdWords' system is based partly on cookies and partly on keywords determined by advertisers. Google uses these characteristics to place advertising copy on pages where they think it might be relevant. Advertisers pay when users divert their browsing to click on the advertising copy. Partner websites receive a portion of the generated income.
AdWords has evolved into Google's main source of revenue, contributing to Google's total advertising revenues of USD $43.7 billion in 2012. AdWords offers services such as pay-per-click (PPC) advertising and cost-per-acquisition (CPA) advertising.