What is Search engine optimization (SEO).?

There are many search engines in the world such as Google, the most famous is Google, then yahoo, Bing, etc. If someone wants to learn Java, he may type in "Java Tutorial" and search the search engine as he may not know the address on a website that has Java tutorial.

Write a Java Tutorial Search Google and many sites will come to Google. Those are Java related sites, but what did Google do? Showing each site down according to their rank. The site that Google first showed. Some strategies were adopted on that site. These techniques are called search engine optimization (SEO).  
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