There is no search engine by its own on internet. Either the organisation behind it provides other services and earn from there or gets a lot of donations.
Search Engine's goal, ultimately, is to make a profit. Almost all see the route to profit must start with satisfied users. They understand that they need to provide their users with the best information possible while making it easy for users. What do they need to do to provide this service? They must: 1. Make money. A business doesn't survive without making money. 2. Have a very large base of pages for their users to search. Some engines now have well over a billion web pages cataloged. 3. Make it easy for the users. If a user can find what they want, they will come back again. This means a good cataloging system, fast response, and hits on what the user wants. 4. Never offend the users. With the exception of a few search engines, they don't want to have pornography, hate groups, violence listed in their engines. 5. Don't support illegal activities. No legitimate search engine really wants to help someone find out how to make poison gas, sell drugs, or provide a pedophile connection.
They usually earn money by placing sponsored ads near search results. Smaller search engines could put affiliate links to Amazon, Ebay, or other stores in those areas if they don't have a large enough userbase.
I would say most of the earning is come from the advertisement, advertiser are paying them to put the advertisement
PPC is the main source of revenue (google). That's why they are strict about relevancy, constantly improving their algorithms etc.. Relevancy is the key, if the advertiser makes money, they sure will keep on pumping cash into the system... The best thing about search engine revenue is that you can make money with just about any topic if we consider that today you have billions of web pages around and millions of them are selling something. Search engines don't choose the niche, they take the money wherever they can. Plus if you add a 60-65 % of the market that google has right now, billions of revenue every year...
Of course by selling ads. Formerly, google not sell anything, they built reputation. After they are established, they sell adsense, and lot other things to get money
I agree with a lot of these people. Google rakes in billions each year off of adsense/adwords. Yahoo has things like their directory that they charge people for, but I'm not really sure how much money they actually make off that.
Search engines are also subsidized somewhat by government. The government started the Internet, not Al Gore.
SE earn by displaying ads such as google ads. Other than that,they gather your personal search behaviour and sell the data to marketing company.