Mobile applications demand several challenges:
a) Keep data on the local device database when there is no reliable internet connection.
b) Upload data to web services to a web database when the internet connection is back.
c) Code once and deliver the app to multi-platform devices like Android and Ios/iPhone.

To address these requirements, several technologies have to work together. Details:
a) WebSQL to keep the data in local storage. Create a WebSQL database, tables and SQL instructions with javascript and JQuery instructions.
b) Ajax (Asynchronous javascript and XML) uploads the data stored locally to web service and saves data on the web database.
c) PhoneGap uses HTML5 and javascript code to generate multi-platform apps that run on Android and iPhone. The framework runs the app inside a microbrowser. Specialized User Interface could fail in PhoneGap. That's why many developers prefer to code in a native platform like Eclipse and Android Studio.
This book develops a complete example to show the concepts of HTML5, mobile database, AJAX to upload data to web server and multi-platform generation with PhoneGap.