What is Online Advertising?

Web advertising differs from other media by enabling consumers to interact with the advertisement. Consumers can click on the ad for more information, or take the next step and purchase the product in the same online session. Consumers can even purchase products from within Web advertisement.
The Internet is a new medium, which allows people to communicate with other people across the world, and to pass & exchange information in large quantities in a short time.
Those abilities, combined with the low cost of communications over the internet, makes the Internet an appealing medium for advertisers, who seek to send their message to as large a number of people, in the shortest time, and for the lowest cost.
The Internet is not a public resource - it's a collection of networks, some paid for and owned by companies, some paid for by various governments [e.g. computers & communication lines bought by tax money for universities], some paid for by private people [e.g. ISPs' equipment is paid for by the subscribers' fees, who also pay for their own computer & phone], glued together into an international network.
So when information flows across the internet from one place to another, the price of transferring the information is split across the originator of the information, the receiver of the information, and possibly one or more other parties who paid for the equipment used in between.

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