Search Engine

What is a search engine?

Search engines are database tools that help users find content on the World Wide Web. Once a user enters a keyword or search query, search engines curate a list of the most relevant webpage URLs, images, or videos, known as the Search Engine Results Page (SERP).


Additional features like auto-suggestions, filters, and advanced search options further refine a user’s search.

How does a search engine work?

Search engines list the most accurate and relevant web pages based on a user’s query or keyword input on the SERP.  In theory, the higher a webpage is on the SERP, the more valuable it will be to the user. Search engines populate the SERP in three stages:


  • Crawling: Automated bots, known as spiders or crawlers, regularly sweep the Internet and “read” web pages. They scan written content, images, videos, and files into the search engine’s database.
  • Indexing: Once webpages are “crawled,” the search engine will begin indexing. Indexing involves categorizing webpages by keywords and queries.
  • Ranking: There are two types of SERP rankings:
  • Organic: Organic search refers to an unpaid SERP ranking. Keyword relevance, webpage popularity, and user experience are known to influence organic search. And while many other factors go into SERP rankings, like backlinks, page speed, and keyword competition, there is no silver-bullet solution for ranking high on the SERP. Search engine algorithms are constantly changing and increasingly difficult to predict.
  • Paid: As the name suggests, paid search results are the top 1-3 SERP spots paid for by companies to run ad campaigns. The easiest way to tell if a SERP result is paid or organic? Paid search results are marked with an “Ad” or “Sponsored” label at the top or corner of their SERP snippet.
What are the most popular search engines?

There are a variety of search engine types that cater to different user needs and web domains. The most common and popular search engine types include:

Mainstream search engines

Free search engines (with paid search advertising) provide users with a broad range of information and content across topics. Google (a mainstream search engine) is still the most popular search engine ever.

  • E.g. Google, Bing, Yahoo!
Specialized/vertical search engines

Search engines that provide specialized search capabilities within one topic or niche.

  • E.g. Medical researchers use PubMed to find peer-reviewed articles
  • E.g. Job seekers use Indeed to peruse mid-tier marketing jobs in their area
  • E.g. Renters use Zillow to find a two-bedroom, two-bath apartment near their work
Meta search engines

Meta Search Engines (AKA aggregators) pull SERP results from several search engines into one hyper-relevant SERP.

  • E.g. Dogpile, Polymeta, SearchSalad

Related Terms

Search Engine Optimization

Search Engine Optimization (SEO) is the practice of optimizing your website to increase the quantity and quality of your traffic via organic search engine results.


Backlinks are links from one website to another. Backlinking is an important factor for SEO that can help improve domain authority and search ranking.

On-Page SEO

On-page SEO is the practice of optimizing web page content and HTML to improve organic search traffic and boost search engine rankings.