Below are some of the actions on a web page that take place server-side.
All kinds of websites use databases to store data on the application server. For example, usernames and passwords will be stored on an application server. When a user types a username and password into a website, the web page will send the details to the server for checking into a secure database.
News websites often include feeds that display data from elsewhere. This means that the web page will automatically update as more news comes in. RSS feeds allow data to be updated on one server and distributed to multiple sites.
A search engine is a web application which keeps a huge database of web addresses. Web pages are stored as an index on a server. When a search term is entered, the server looks through an index of web pages that contain the term. The box that the user writes the search word into is like a form that is used to run a query in a database. Search engines use server-side processing to find and deliver the search results.
The index has already been put together by an automated program called a crawler that is run by the search engine program. The crawler frequently visits web sites and takes a record of the address and keywords and adds this information to a database with an index. The index links the website to other websites that are connected through hyperlinks.
Different search engines have their own crawler programs and algorithms so a search in one engine might produce different results to another. Web pages appear higher up a list of results because they are judged to be more important by the search algorithm. Their importance is measured by the popularity of a site and how many connections it has with other websites.