What's a search engine?

A search engine is an application used to locate web pages or other files based on keywords entered by the user.

It is able to do so because of phrases or text strings in the HTML code that are called Meta Tags.

The most common meta tag is the one called Keywords.

If your web page contains the text "How to build a website," then your Keywords meta tag could be:   Meta Name="keywords" content="how, build, website" or so on.

Why would you need one?

Search engines make it possible to find websites containing the content you are looking for much more rapidly than if you had to read the whole page.

They act much like the Edit - Find feature in your browser except at a website level instead of a page level.

Also, if you don't know the name of a website that contains your query, the search engine can provide from zero to millions of relevant or irrelevant web pages, so keywords make your results more usable.