Many folks confuse what a web application & what a mobile application are.....

A web app is an environment that keeps a database structure in order to produce content usually known as a CMS.

A mobile app is a bit different, mobile applications are mostly a local environment meaning it stores all the information (data) unto ur device.

Space is a HUGE fact when building for any device...

But web apps never worry about space nor does a web app becomes specific to one type of device or browser.