Google AdWords is an online advertising service in which advertisers pay to display brief advertising copy to web users, based in part on cookies and keywords predefined by the advertisers. Web pages from Google and from partner websites are designed to allow Google to select and display the advertising copy selected. Advertisers pay when users divert their browsing to seek more information about the copy displayed, and partner websites receive a portion of the income that is generated.
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 pay-per-click (PPC) (cost-per-click (CPC) advertising), cost-per-acquisition (CPA) advertising, cost-per-thousand-impressions, or cost per mille (CPM) advertising, site-targeted advertising for text, banner, and rich-media ads, and re-marketing (also known as re-targeting). The Ad-words program includes local, national, and international distribution.