allows them to compete against other advertisers in a private auction hosted by a publisher or, more commonly, an advertising network. Each advertiser informs the host of the maximum amount that he or she is willing to pay for a given ad spot (often based on a keyword), usually using online tools to do so. The auction plays out in an automated fashion every time a visitor triggers the ad spot. When the ad spot is part of a search engine results page (SERP), the automated auction takes place whenever a search for the keyword that is being bid upon occurs. All bids for the keyword that target the searcher's Geo-location, the day and time of the search, etc. are then compared and the winner is determined. All this happens in real time, therefore this is called real-time-bidding or RTB, and in a fraction of a second. In situations where there are multiple ad spots, a common occurrence on SERPs, there can be multiple winners whose positions on the page are influenced by the amount each has bid and the quality of their ad. The bid and Quality Score are used to give each advertiser's advert an ad rank. The ad with the highest ad rank shows up first. The predominant three match types for both Google and Bing are Broad, Exact and Phrase Match. Google Ads and Bing Ads also offer the Broad Match Modifier type (although Google retired it in July 2021) which differs from broad match in that the keyword must contain the actual keyword terms in any order and doesn't include relevant variations of the terms. In addition to ad spots on SERPs, the major advertising networks allow for contextual ads to be placed on the properties of 3rd-parties with whom they have partnered. These publishers sign up to host ads on behalf of the network. In return, they receive a portion of the ad revenue that the network generates, which can be anywhere from 50% to over 80% of the gross revenue paid by advertisers. These properties are often referred to as a content network and the ads on them as contextual ads because the ad spots are associated with keywords based on the context of the page on which they are found. In general, ads on content networks have a much lower click-through rate (CTR) and conversion rate (CR) than ads found on SERPs