how does search engines earn revenue and why it is free of cost for public?

[narrowcelery837]

how does search engines services and social networking sites generate revenue and manage service at free of cost to customers?
i tried searching about this information on search engine i couldn't find reasonable answer .

[Mr B]

They earn revenue through advertising (Sponsors Ads on Google Search...)

[Steez]

They manage to keep the site running by advertisements. advertisements pay the runners of the site to be able to advertise on their site. Users get to use it for free but see ads everywhere because the ads are trying to get you to buy tgeir product. But like i said sites are free to the user and keep running because advertisers pay them to advertise on their website.

[Smarty]

search engines earn revenue depending on the number of people visiting search engines n clicking or viewing further pages n also through adds.