In this lesson I want to answer a core question: What is Search Engine? I’ll define it in my own words, explain why it’s more complex than a phone directory, show the market leaders, and walk you through how search engines add websites to their database.
My aim is to give you a clear, practical view so you can focus your SEO efforts where they matter most.
Table of Contents
- What is Search Engine and how would I define it?
- Why is a search engine complicated despite sounding simple?
- How does a search engine work step-by-step?
- Which search engines dominate the market in 2021?
- How does a search engine add new websites to its database?
- How should I prioritize SEO given how search engines work?
- Conclusion: What is Search Engine and why it matters for your site
- Frequently Asked Questions
- Final thought
What is Search Engine and how would I define it?
To me, a search engine is a platform where you type what you want to learn and it presents relevant information from its database. That definition sounds simple — like a web or phone directory — but the difference is the scale. The search engine database is essentially the World Wide Web, and that adds an enormous layer of complexity.
Why is a search engine complicated despite sounding simple?
Here are a few numbers to show the scale: there are more than 1.1 billion websites on the internet and search engines index at least 5.5 billion web pages. Google alone processes over 40,000 queries per second — almost 3.5 billion searches a day. When you know these facts, you can imagine the practical problems a search engine needs to solve:
- How do we find all the web pages on the internet?
- How do we store that huge amount of content?
- How do we retrieve the right pages for a query quickly?
- In what order should results be displayed?
- How do we present results for a great user experience across devices and languages?
- How do we manage millions of users at the same time?
How does a search engine work step-by-step?
The full process is very complicated, but at a high level I simplify it into five steps so you can get a practical understanding:
- A user visits a search engine.
- The user types a search query.
- The search engine scans its database (index).
- Using machine processes and human guidelines, the engine finds the best results.
- The user is presented with a ranked set of results that aim to match their intent.
This sequence — query, scan, rank, present — is the overall flow that powers every search you perform.
Which search engines dominate the market in 2021?
When you ask What is Search Engine? you also need to know which engines matter for SEO. As of 2021 the market share looked like this:
- Google: ~91.86%
- Bing: ~2.71%
- Yahoo: ~1.46%
- Baidu (China): ~1.13%
- DuckDuckGo (privacy focused): ~0.66%
- Yandex (Russia): ~0.087%
Because Google is the clear leader — it indexes hundreds of billions of pages and received tens of billions of visits in recent years — it makes sense to concentrate most SEO effort there. I focus primarily on Google in my teaching, but I also recommend you consider Bing and Yahoo as secondary targets since they can share databases and appear as defaults on Microsoft devices.
How does a search engine add new websites to its database?
Adding websites to the search index involves three core stages: crawling, indexing, and serving results. Let’s break each down the way I explain in this lesson.
What is crawling and how do search engines discover pages?
Crawling uses automated programs — often called web spiders or crawlers — that continually search the web for pages. The most common way crawlers find new content is by following links from pages already known to the engine. This ongoing discovery process helps search engines keep their index fresh.
What is indexing and what information is stored?
Indexing happens when the search engine visits pages discovered by crawlers and analyzes the content: text, images, video, PDFs and more. The engine determines each page’s topic, catalogs it, and stores a cached version in the search index so the page can be retrieved later during a query.
How are search results served to users?
Serving results is what happens when someone searches. The engine pulls the most relevant and useful results from its index and displays them. Which pages are considered “best” depends on many factors including: the searcher’s location, language, device, preferences, the search engine’s ranking algorithms (the rules), the user’s intent, and SEO competition.
How should I prioritize SEO given how search engines work?
Because Google controls most of the market, focus your primary SEO work on how Google crawls, indexes, and ranks pages. At the same time, make sure your site is accessible and technically sound for other engines like Bing and Yahoo — this includes clear links, structured content, and fast loading pages so crawlers can find and index your pages easily.
Conclusion: What is Search Engine and why it matters for your site
In this lesson we covered what a search engine is, why it’s complex, the top search engines in the market, and how engines add websites to their database. Remember: search is a system that needs to discover, store, and serve billions of pages quickly and accurately. If you understand that flow — crawling, indexing, and serving — you will be better at making practical SEO choices that help your site appear where users are searching.
Frequently Asked Questions
What is a search engine?
A search engine is a platform that lets you search for information and returns relevant results from its database, which is effectively a catalog of web pages collected from the internet.
How does a search engine add websites to its database?
Search engines discover pages by crawling links, analyze the content during indexing (text, images, video, PDFs), and store that information in a search index. When a user searches, the engine serves results from this index.
Which search engines should I focus my SEO on?
Primarily Google, because it owns the majority of market share. Secondarily consider Bing and Yahoo, especially for users on Microsoft devices or niche audiences.
What determines which results a search engine shows?
Results are ranked by many factors: user location, language, device, user preferences, the search engine’s ranking guidelines and algorithms, user intent, and the quality and SEO of competing pages.
How often do search engines crawl and index pages?
Crawling frequency varies by site and page importance. Popular or frequently updated pages are crawled more often. The engine decides crawling schedules based on many signals, including link structure and site changes.
Final thought
Understanding What is Search Engine? is the first step to practical SEO. If you build accessible, well-structured content and think about how crawlers and users will find and use your pages, you’ll be in a strong position to rank and serve the people who matter to your business.
