Chapter2.How Search Engines Work

Chapter 2. How Search Engines Work

You type a few words into Google, and you get a screen full of highly relevant results in seconds. But how did it happen? How does a search engine find the right pages? You have learned that search engines return both organic and paid results, and we repeat a figure shown in Chapter 1, "Why Search Marketing Is Important … and Difficult," as Figure 2-1.

Figure 2-1. Types of search results. The Google search results page clearly separates paid from organic results; other search engines combine them.

In this chapter, we examine exactly how a search engine works, showing both what happens at the time a searcher enters words to be searched and what happened beforehand to prepare the search engine for that search. We spend most of our time on the more complicated organic search, but we explain how paid results are chosen, too.

Although it looks like Google is scanning each and every Web page the moment it displays your organic search results, it is not really that magical. It turns out a lot of preparation led up to that "magical" moment when the words are searchedsearch experts call that preparation indexing. Indexing is the process that creates a search index, a special database that holds a list of all the words on all the pages on the Web. Later in this chapter, we explain how the organic indexing process works. For now, just be aware that a lot of the magic of organic search engines occurs long before anyone enters anything to search.

Without yet knowing how the search index is created, you can still learn how the organic search engine uses that index when search words are entered. At the moment that words are typed into Google, the search engine does three major things, as shown in Figure 2-2:

• Matches the search query. The search engine must analyze the words the searcher typed in and pick the pages that match those words.

• Ranks the matches. Most search queries return many matches, so the search engine must sort the matches so that the best ones are at the top.

• Displays the search results. After the best matches are chosen, the search engine displays them on the screen for the searcher to see.

Figure 2-2. How organic search engines work. Every search engines matches search queries, ranks the matches, and displays them as search results.