This blog is about How does a search engine works, what actually goes behind them and what are the different types of search engines.
Before understanding how does search engine works Let we first understand what is search engine.
> *search engine is a software program which is design to identify*
> *respond to specific questions called keywords and populate the pages*
> *called as SERP (search engine results page) with the relevant*
> *information available on the web.*
We have millions and billions of websites available on web and when we want to access it then we have only one source that is search engine.
Search Engine refers to a huge database of internet resources such as web pages, newsgroups, programs, images etc. It helps to locate information on World Wide Web.
Basically what do search engine?? Search engine respond to a certain question that the user has posted is called **keyword**. When we type a query in search engine then it breaks into small segments.shown in below image..
![How does search engine works]
It actually search the relevant information related to that particular keyword from web ocean and displays that information. Display of information that you see in the search engine is called as a SERP search engine results page .This is basically how the search engines work.
Now let's understand into what actually goes behind it and what are the steps and key factors that it is using for search and display the results.
**Actually search engine works into three basic steps.**
## Crawling (discover content) ##
Before understanding crawling process first we understand what is crawler or spider.
> *A spider, also known as a robot or a crawler, is actually just a*
> *program that follows, or "crawls", links throughout the Internet.*
> *Search engine uses web crawlers to discover publicly available web*
> *pages in the web (www).*
*In simple words we can understand crawling as a process to discover all contents available on web by following the links available on web pages.*
![crawling by robot of search engine]
Spiders only can reach from one site to other site and one page to other page through the links. That’s why links to your site (**inbound links**) are so important.
Links to your website from other websites will give the search engine spiders more "food" to chew on.
The crawling process begins with a list of web addresses from past crawls and **sitemaps** provided by website owners. As crawlers visit these websites, they use links on those sites to discover other pages.
## Indexing (analysis and stored ) ##
The first thing to understand is that when we do a search we are not actually searching the web, we are searching index of the web.
So Before you search, spider gather information from across hundreds of billions of web pages by crawling and organize it in the Search index.
![indexing process by search engine]
> *when web crawler find a web page it render all content of web page*
> *just like a web browser. After rendering a page it collect all data*
> *related to that page like available keywords, website freshness,*
> *domain related information etc and make index of it and stored back*
> *into database.*
When web crawler find a web page it render all content of web page just like a web browser. After rendering a page it collect all data related to that page like available keywords, website freshness, domain related information etc and make index of it and stored back into database.
It just similar like making a list of all the books you own, their publishers, their authors, their genres, their page counts, etc.
The [Google Search index] contains hundreds of billions of **web pages** and is well over **100,000,000 gigabytes** in size. It’s just like the index in the back of a book — with an entry for every word seen on every web page are indexed.
So at last we can understand indexing as process to analysis a webpage and stored it into database for further use.
## Retrieval ( fetched and display ) ##
Third step is, fetching data from the search index and deliver it to user in an order. For which different algorithm are used.
**PageRank** ( made by google) is the best known algorithm which is used to improve web search results. PageRank was named after **Larry Page**, one of the founders of Google. PageRank is a way of measuring the importance of website pages.
**"This is section where SEO comes into picture."**
According to [Google]
> **PageRank** works by counting the number and quality of links to a page
> *to determine a rough estimate of how important the website is. The*
> *underlying assumption is that more important websites are likely to*
> *receive more links from other websites.*
![Retrieval ( fetched and display )]
Search engines also pay attention to lots of other ‘signals’ when working out the order to show results. For example how often the page is updated and if it is from a trustworthy domain, how
many times does this page contain searched keywords, do the words appear in the title and the URL directly adjacent does the page include synonyms for those words, is this page from a quality website or is it low quality even spammy.
Google consider more than [200 factors] during retrieval process.Finally combining all these factors search engine give rank to web pages and show it to user within less than a seconds.
> *[Google] covers more than **90%** of Search Engine Market Share Worldwide*
## Following are the several search engines available today: ##
| Search Engine | About |
|Google | It was originally called **BackRub**. It is the most popular search engine globally.|
|Bing | It was launched in 2009 by **Microsoft**. It is the latest web-based search engine that also delivers Yahoo’s results.|
|Ask | It was launched in 1996 and was originally known as **Ask Jeeves**. It includes support for match, dictionary, and conversation question.|
|AltaVista | It was launched by **Digital Equipment Corporation** in 1995. Since 2003, it is powered by Yahoo technology.|
|AOL.Search | It is powered by **Google**.|
| Alexa |It is subsidiary of **Amazon** and used for providing website traffic information.|
Source:- [tutorial point]
## Conclusion ##
All search engine work on different algorithm so search result of one search engine may differ with other.
![Famous search engines]
> *Thousands of engineers and scientists are hard at work refining search*
> *algorithms and building useful new ways to search*.
Search algorithm are changing day by day. You can understand it by these thing that **1600 improvements to Google Search in 2016** alone, these are just a sample of some of the ways they have been making Search better and better over time.