Although HTML and CSS are very powerful together, with just those two entities the web would be a realm of static pages. The only interactions we could accomplish would be to click on links to other static pages. No user accounts, no paying bills online, and forget about social media altogether.
The powerful technologies that make up the rest of the web consist mainly of databases and additional processing languages. Databases allow information to be stored and processing languages allow developers to access information in those databases. These technologies are important because they keep information secure, save time, and allow end-users to update content easily without having any development experience at all.
Content management systems are built on databases and processing languages. Many of the popular content management systems are built on MySQL databases along with PHP, including WordPress, Drupal and our personal favorite, MODX. A database is really just a sophisticated table of information. With languages like PHP, one can access information from those databases and accomplish tasks such as verifying usernames and passwords, updating site content, and much more.
The web can be an intimidating world or acronyms and jargon. It is evolving at a rapid pace. However, the basic essentials remain the same as does the intent of sharing information with one another. We hope what we shared helps clear things up a bit.