All webiste stores, message-boards, and Content Management Systems (such as WordPress) use this technique. The contents of the page is stored and retrieved from a database, and the rendered on the screen for the viewer to see. This usually happens "on the fly" as each page is displayed.
The advantages of this to the viewer is that the content can be selective and show them only items that they might be interested in. The advantage to the website owner is that the content can be edited and published by many members of staff. Fresh material appears dynamically on the page.
People visit websites with all sorts of devices now days. Gone are the days when the only device was a PC or a laptop. Mobile phones, TVs, Tablets all have to be considered now. The biggest problem with these devices is that the screen size is different for each. Some have relatively very small screens. Nobody wants to scroll left and right, up and down to view content.
With some clever trickery behind the scenes, a website can be designed to adapt itself based on the size of the screen being used. Blocks can be displayed differently, or even hidden if the screen is very small.
The key to modern website design is that the design should work well on the small devices - plan for them first, then allow the pages to expand and fill the screen if it is larger.
Here is an example of a database driven website. The TV Listings site collects TV listing data from a free source and stores it in a database.
Once a user has told the system which channels they receiver, the system can search the listings.
The user can add wish lists as well. Each morning the system will search through all the fresh data to see if any of the items in the wish list appear. If so, then an email is sent showing these details, allowing the user to set their own recorders to record the item.