Before defining WAP, we must first understand why we need it at all. The answer lies in the limitations of a mobile device as compared to a computer. A computer here refers to a desktop or a laptop and mobile devices refer to cell phones and tablets.
These files are essentially websites. Now, how do you view the same websites with that 3-column layout and large images/video, etc on a mobile device with a much smaller screen, limited bandwidth, small memory & a much weaker processor?
You need to replace the website with a version that fits into the limitations, right? That’s exactly what WAP does. Like HTTP, it allows users to access the files on the server, where these users are “mobile device” users and not “computer” users.
That being said, there are also a number of other additions & modifications defined by WAP. Together, all these changes can be defined by a Layered Reference Model of the WAP. These can be viewed as replacements of various layers of the Internet/WWW. Here is a camparison of the two:
The ones in blue are the WAP replacements for mobile devices. They replace the ones in green which are for the internet/www on computers. This model allows mobile devices to display websites optimally despite its limitations as compared to a computer.