A search engine is an online tool that searches for results in its database based on the search query (keyword) submitted by the internet user. The results are usually websites that semantically match with the search query.
Search engines find the results in their database, sort them and make an ordered list of these results based on the search algorithm. This list is generally called the search engine results page (SERP).
There are many search engines on the market, while the most widely used is Google. Many website browsers such as Chrome, Firefox, Safari or Edge usually come with a default search engine set as a home page or starting page.