With an increase in the number, diversity and complexity of smartphones, more and more companies want to have their own mobile app, but creating a native app can be pretty expensive. It requires special skills, as well as special coding tools, and then there is also the need to build an app per platform (Android, iOs, BlackBerry, Windows Phone, etc).
All of this figures in to a higher price tag for the app development. Another solution for developers is then to create something called web-apps: HTML CSS apps, which users can access from their browsers. They are cross-platform, and cross device.
The jQuery framework has been around the web for a while now, but the jQuery base technology was basically designed for browser apps. jQuery Mobile is a framework based on jQuery that enables web designers to create web-apps that are optimized for use on a mobile device (Smartphone and tablets). The framework is touch optimized, uses responsive layout so that elements will automatically adapt on different device sizes, and supports a range of different platforms and devices.