Pay per click (PPC) is an Internet advertising model used on search engines, advertising networks, and content websites. The main benefit of PPC is that advertisers only pay when a web user actually clicks on an advertisement to visit the advertisers' website. Pay per click is based on an auction model, where advertisers typically bid against competitors on keyword phrases relevant to their target market. When a user types in a keyword query matching an advertiser's keyword list, or views a webpage with relevant content, the advertisements are then displayed in an order depending on a number of criteria including maximum bid and advert quality rating. Such advertisements are called sponsored links or sponsored ads, and appear adjacent to or above the 'natural' or organic results on search engine results pages, or anywhere a webmaster or blogger chooses on a content page. Content websites commonly charge a fixed price for a click rather than use a bidding mechanism.