How search engines work
Search engines like Google, Bing, or others rely on complex algorithms to organize the endless information and data on the web.
Search engines index the "Page Index" pages that they identify by their URL and through which the content and whereabouts are known.
The engine also keeps a copy of the indexed pages, so it can easily find them in the future, and you can index your site through my Google URL Inspection Tool.
After this, the engine crawlers, and spiders are responsible for it. Spiders follow the links between each page and the next, so all the pages on your site must always be interconnected so that the engine can find them.
After the process of crawling and indexing that the search engine does, it starts displaying the results according to their compatibility with the researcher's question, and of course, the results that correspond the most occupy the first positions.
Most Popular Search Engines

Search engines help users to access information on the Internet, whether the results are articles, research, videos, images, other search suggestions, etc.
The popularity of search engines varies from place to place according to the needs of individuals, markets, services provided by these engines, and the extent of their development, and Google often leads the search engines in most if not all countries of the world.
Google
Google is the most popular search engine in the whole world, as it relies on complex algorithms and is constantly working on developing crawling and indexing methods for sites.
It also excludes inappropriate sites, annoying sites, or "spam", but at the same time, if the site is not compatible with its algorithms, it will not display it in the search results.
It is also characterized by having a lot of extensions or tools that make it easier for users, as well as applications for devices and phones, which makes it the first choice for more than 90% of researchers.
But the competition between sites on it is the largest, the site must work to develop itself continuously to appear in the first results in the search engines.
Bing
It is the second most popular search engine in the world, and it is produced by Microsoft after it integrated it with the "Microsoft Edge" browser, and they are working on developing it continuously.
Bing is distinguished by its research in matching images and videos and its answer to the equations presented to it. When researchers put an arithmetic problem with a knot, he answers it or displays sites that answer the same question.
It is also possible to make lists to save the sites or pages that you want to record or refer to from time to time.
Although sites and pages on it are fast in their performance, it is slower than Google in displaying its results and often inappropriate for the researcher's question, and not all of its results are reliable.
Yahoo
It is one of the most famous and oldest search engines, but it has returned to competition again after its decline in the past years and is distinguished by its presentation of free results "Organic Results", as well as the purchasing search "Shopping" and application services and mail.
But it has a lot of ads and doesn't tell the difference between free and paid results, and it doesn't show results history.
Yandex
Yandex is one of the most popular search engines in the Russian market even before Google, it leads the Russian market with a share of more than 50%.
According to Stat-Counter indicators, since mid-2019, Google has had the largest market share, at about 52%, compared to 45% for Yandex.
It is also popular in Turkey, Ukraine, China, Germany, Belarus, and Kazakhstan, so it is a suitable search engine when targeting Central Asian and Eastern European countries.
It is available in both English and surreal and is characterized by the provision of high-tech services in addition to its smart and high-quality products, and its results are locally relevant, and it can also be customized to know the results of specific countries.
It also has a premium image search, but it collects user data like other search engines.
Baidu
Many call it "Chinese Google" as it takes up most of the Chinese market, and most of its users are from China, and it is popular among users who are interested in Asian markets.
Its results are distinguished by their high quality, and the most prominent shortcomings come in the questions related to the integrity of the results imposed by government oversight on it.
DuckDuckGo
DuckDuckGo does not have its own engines like Google and Bing, but it relies on a lot of sources for its research, and it is constantly evolving.
If you are looking for privacy and do not want ads to appear whenever you search for something, then DuckDuckGo is definitely the best option because it does not track, collect or store user traffic, their slogan is the search engine that does not follow you.
It displays ads but it is not personal, and its search page is easy and displays results very quickly and on the same page, but its results from images are limited.
Summary
SEO is the improvement of search engine results for the appearance of the site on the first page in the SERP to reach the largest number of target customers.
When working on the SEO of your site, you should take into account other search engines because this will help you appear on the first pages and thus reach your target customers faster and more.
Also, when targeting diverse markets, you can display your ads on the search engines that occupy the second and third positions, as the competition between them is close, as the cost of advertising on them is often lower than the cost of advertising on Google.