How Search Engines Work
We use them to search for information on the web every day; you type in a query, you get back links to answers (or get the answers directly sometimes). But have you ever wondered how these “answer machines” come up with answers? Well, it’s time we found out by looking at the inner workings of search engines.
First off, the term “search engine” is a general term used to describe both human-powered search engines (or web directories) and crawler-based search engines. Although they do the same job (providing answers to user queries), the way the two go about it is radically different.
Crawler-based search engines
Crawler-based search engines have three main elements: The spider or crawler, the index, and the search engine software. Spiders visit the different websites on the web, read them and use the links on those sites to find other sites. Information gathered by the spider is then stored in an index, also referred to as a catalogue.
The search engine software then sorts through all the recorded pages and matches them to searches before ranking them based on how relevant it “thinks” they are.
Crawler-based search engines such as Bing and Google work this way to create listings automatically. What this means is that they “crawl” the web using spiders, index the information, and then allow people to search through the information they have found.
Spiders return to crawled sites regularly to check for changes and updates that might have been made to sites and add this to the search engines database automatically. This could affect how your site is listed.
Web directories such as Open Directory, on the other hand, depend on humans for their listings. Website owners have to submit short descriptions of their entire site to the directory for their site to be listed. Editors for the directories could also add descriptions for the sites they review. A search using a directory will only bring up answers from submitted descriptions.
Changes to your website will have no effect on your listing as the information contained there is more or less static unless changed manually. This means that SEO strategies will have no direct impact on listings in directories.
So how do crawling search engines determinerelevance?
To search engines, determining relevance is more complex than matching words from a search query with words in the content of a web page. Of course, earlier search engines worked this way which produced results of limited value. Engineers over the years have come up with better ways of matching results to search queries with numerous factors influencing relevance.
Some of these factors include backlinks from other websites, keywords (to a limited extent), and social media metrics among others.
Search engines also assume that popular documents, sites, and pages must contain valuable information hence the large amount of traffic. The notion has proved to be true most often than not and has helped determine relevance as well.
Search engines play a big role in helping us find what we are looking for on the internet. Without them, the internet would be one big mess of information that cannot be readily accessed. Search engines are, therefore, not only answer machines that provide answers to our questionsbut crucial elements of the internet without which web surfing would be extremely difficult.