How do search engines work?
Search Engines like Google or Bing work by creating an index of all of the sites on the internet and reading through them to find out what they are about. Based on the results they determine they attempt to find out the website that would be most relevant to a particular search term or query like “Where can I buy red shoes” and show the results in order based on how relevant they are to your search.
In order to do this they send out programs to read through millions of websites and record the words and phrases contained on these sites. They also monitor factors such as:
- How long the site has been in existence
- How many pages does the site have that mention each word or phrase
- How often this content is updated or added to
- How often people read the content
- How often people see this page and then leave immediately (known as a bounce and typically indicates they didn’t find the answer they were looking for)
Based on this they compile an index. Now when you search for “Where can I buy a hot dog?” or some similar query, they can look through their index and select out all websites that talk about hot dogs. Then they look through and see which ones actually offer hot dogs for sale. They might also detect where you are physically located when you are doing the search and select all of the websites that are for businesses located close to you.
Remember that they are collecting a lot of different factors, not just what words and phrases are on your site. These factors such as, how long has the site been up, how often does it get updated, how long do people normally spend on the site, etc, get evaluated against a system of measurement known only to Google and they use the data to try and determine which sites would be the best answer for your query. Their goal is to provide the most accurate results for the person searching for answers.
After all of this filtering, they still might have a large number of websites that fit all of these points. In some cases it might be hundreds of thousands or more results! Yet when you look at the page that shows the results of your search, only 10 results show up per page. So how does Google know which results to show on that first page and in what order?
Once they determine this, they will then show the results in the order of which sites they feel are the most relevant answer to the query. They constantly review the sites in their index and regularly add new ones so they can continue to provide the best answer to people using their service.
You might ask, “why do search engines do this?” Or “What do they get out of it?”. The answer is simple, the better the search engine, the more people use it. The more people use it, the easier it is for them to sell advertising on it. “How does online advertising work?”