A universal app is a single app that works on iPhones, iPod Touches, and iPads. This gives the optimum user experience without the need to download two distinct versions of software.
When a user launches the universal app on an iPhone, the iPhone version appears.
Before Apple introduced the universal app concept, developers generated two binaries: one for iPhone and one for iPad. You can design a single binary that works on various iOS devices with multiple screen sizes with a universal app.
Xcode simplifies the process of creating universal apps. You may develop user interfaces in Xcode using either Interface Builder (a nib file) or Storyboard. Depending on the UI design method you pick, the process of designing a universal app varies.