Your question is “How does Search Engine collect all information from various websites across the World Wide Web?” Well, Let’s discuss.
Search Engines have emerged as a powerful and important tool that makes the job of surfing the net a much easier task. Imagine, if there were no search engines, then we would have to keep a record of a variety of websites as per our needs.
But within a Search Engine, all one has to do is to type in a keyword or a few keywords and it presents before us a list of possible websites which might be of our interest.
The internet contains billions of websites. At a given time it is nearly impossible to scan through all the websites and their content. Search Engines use web crawlers and indexing to maintain the database of websites.
Depending on the keywords searched, the Search Engine ranks and displays relevant pages on its SERP (Search Engine Results Page). This is discussed in detail below in this article.
Initially, Search Engines used primitive ways to rank search results. But people learned techniques to bypass those ranking criteria or game the Search Engine (SE).
Now as a result of it, over the years, Search Engines have become sophisticated and better in their search techniques so as to satisfy a user’s query. The task before search engines is humongous as the internet has billions of websites and tons of content.
How it all works?
On the basic level, Search engines could be classified into three types: SEs using robots (called web-crawlers or spiders), SEs depending on human submissions, and SEs which are a hybrid of the two.
Web-crawlers are software applications that can run automated tasks or scripts over the internet. Search Engines have their own web crawlers, which might have specific tasks assigned to them. These robots read a site’s Meta tags and also follow the links that the site connects to.
Through these links, the web-crawler performs indexing on the linked sites as well. Each webpage recommended after a query on the Search Engine means that the webpage had been visited by the Search Engine’s web-crawler.
Once the crawler gathers the information, it returns all the information back to a central repository or a database.
It is at this central database of the Search Engine where all the data is indexed. The web-crawlers perform this job continuously over all the websites over the internet. The web-crawler also periodically returns to websites to check for any changes in information or content.
The frequency with which a web-crawler would re-scan a website would be determined by the administrators of a Search Engine. In some cases, websites might disable web crawlers from visiting them. These pages will be left out of the index, along with pages that no one links to.
On the other hand, as obvious it is, Human-powered search engines depend on humans to submit information. Only information that is submitted is put to the index.
Whenever a user searches for some information on the Search Engine by typing in some keywords, he is not actually searching the Web but instead, he actually searches through the index which the Search Engine has created.
These indices are humongous databases of information that are continuously collected, updated, stored, and ultimately searched. A considerable time may lapse between two re-indexing a page, and in the meanwhile, if that page has been removed or has become invalid, dead links may be encountered as a result of it.
This means the Search Engine still treated that page as still an active link even though it no longer remained as such.
It may also be the case that the same search on different search engines might produce different results on that Search Engine’s SERP. A partial reason for this is that not all indices prepared by Search Engines be exactly the same.
This depends on what fundamentally different (of different search engines) web-crawlers explored and sent back as information for indexing.
This is also because different Search Engines use their own set of diverse algorithms to search and rank through these indices. The algorithms are used by Search Engines to decide the relevance of the information in the index to what the user is searching for.
Google’s Search Engine, for instance, uses algorithms such as Panda, Penguin, Pirate, Hummingbird, PageRank, Pigeon, etc. Each of these algorithms focuses on different aspects of a page such as content, backlinks or link-building, content’s uniqueness, distance and location in case of local organic search results, etc.
These different algorithms enable Google to decide a page’s relevance, authority, trustworthiness, etc. with respect to a user’s search query; as the ultimate goal of a Search Engine is to satisfy the user’s search.
The algorithms also help Search Engines not only to show relevant results but also to filter out irrelevant, invalid, and spam results. Over the years, the algorithms have been fine-tuning to recognize any ill or manipulative practices by webmasters to take advantage and improve their rankings by violating search engine’s guidelines.
Once it has been decided which practice had triggered an algorithm, the website/webpage might be penalized. Once penalized, the website might lose its rankings. Or if the violations are serious and repetitive, the algorithm may cause that page to be de-indexed which means those pages would not appear anywhere in the SERP.
The algorithms have become such advanced that in most of the cases now, they are also able to understand the intent behind a user’s query. So even if one might not have typed in the exact keywords, the Search Engine might still display what we might have intended to search for.
In conclusion; a complete combination of factors and actors such as web crawlers, giant databases, Search Engine guidelines, a variety of algorithms, etc helps a Search Engine to collect all information from various websites across the internet. Once the information is gathered it is suggested in the SERPs according to various criteria so as to satisfy the user’s search intent.