Search engines work in mysterious ways. But no matter what search engine tries to show you, they have two major functions: crawling and building an index, and providing users with a ranked list of websites created according to their queries.
The internet and the World Wide Web can be described as a huge network. The network is connected to other networks with many nodes - each representing a unique identity. As more people are using the internet, the World Wide Web is increasing in size.
Each and every part of the web, connected by the inter-connected network, has to stop somewhere. The stops are unique contents (a page, or any file). And what search engines do is to pass through all the networks they are allowed in order to find all the stops they manage to stumble upon along their way.
And what helps search engines go to one place to another is links. These are they path in which search engines follow in order to travel from one place, one network, to another. These links are the structure that bind pages together.
Crawling and Indexing
Billions of new contents are uploaded on the internet. Each of these contents are the stops in which search engines must crawl and index to keep their database updated. Google and other search engines are crawling billions of documents, pages, files, medias and many other thing on the World Wide Web.
Links allow the search engines/automated robots, called "crawlers" or "spiders," to reach the many billions of interconnected nodes and stops on the web.
Once the search engines find these pages, they decipher what they "see" in them, and take selected pieces to store them inside their database, only to be recalled later when someone use the search query. This is what search engines are all about. They come when they're expected, they see what they understand, they take what's needed, and all that in order to deliver the information to people that wants them.
To accomplish the task of holding billions of pieces of data, search engines are working hard to improve their algorithm, their systems, their hardware and more, to give results faster and better. A few seconds delay in delivering an answer for a search query can translate to user dissatisfaction.
Answering the Query
What good can a search engine be if it couldn't give a result to a given query? When you go to search engines, you're obviously want to search for something. What search engines do is trying to give the most relevant answer to your needs (query) by understanding each words you type, and compute it as a sentence if possible, and filtering them according to the information they have on you. All of these is to give you the best answer.
And to make sure you get what you want as fast as possible, search engines initiate the task in fractions of a second.
This makes search engines an answer machines. Behind the scene, when you perform an online search, search engines digs into its corpus of billions of data. First, it returns the results that are relevant and useful to you, and second, it ranks those results according to its popularity of the given website that host the information.
Both relevance and popularity are the process of SEO to influence.
Determine Relevance and Popularity
Search engines understand the query you ask them by understanding the words you say by terming them as keywords (long tail and short tail keyword). But to them, finding relevance is more than just finding a page with the correct words.
Back in the early days of search engines, they didn't go further than this step, and search results they create were limited in value. When search engines mature, they came up with better ways to match results with queries.
Modern search engines typically assume that the more popular a site, page, or document, the more valuable the information it has. Search engines use their algorithm to first sort data to find relevance, then rank them in order of quality to find popularity.
In order to achieve this, search engines' algorithms use hundreds of variables, also called "ranking factors".
According to Moz that surveyed leading search marketers, has provided its opinions on ranking factors seen below:
Built and Meant for People
The internet is as crowded as it can be. When bots are taking a larger role on the internet's activity, beating humans in their number of traffics, search engines are not meant for them. Search engines were created by humans to serve humans, and humans only.
One of the focus of search engines is to deliver what the audience want, whenever they want.
When you type a query into a search box and land on a website, search engines are hoping that you'll be satisfied with that you see. This is the primary question that search engines are trying to answer billions of time a day. Its their responsibility to deliver the most relevant answer to their user.
And all of that starts with words typed into a small box.