Static content is a plain html file that doesn't change for any user or request. The same content is displayed to everyone, regardless of anything else including variables, sessions and cookies. Dynamic content, on the other hand, is specifically displayed based on a web browser's request. It can change the whole way information is displayed, from listing only 5 articles on a page instead of 10, or listing them alphabetically or by article ID (incremented upon insertion to a database) or by the date last modified. This control makes dynamic web pages very attractive to web designers.

If your site has information about a product or service, or just anything that isn't likely to change, static pages are great. However, if the content changes frequently, adding a PHP backend to your site to control the content may be the way to go. You might also look into Content Management Systems.