I spend most of my time creating Android apps using Java and the Android SDK. That’s a development style that fits my experience and interests.
There are lots of developers out there who have great skills in web-based technologies like HTML, JavaScript and CSS; many of those developers are looking to start creating mobile apps. The good news is that there’s a now a solution for just those developers.
Fellow Pluralsight author, Shawn Wildermuth just created a course for just those folks: Practical PhoneGap. It doesn’t completely replace traditional mobile app development but does work well in a number of situations. Here’s the description from the Pluralsight website…
App development is crucial to succeeding in most jobs these days. Even if you aren’t building apps directly, you’ll likely be involved in the app development process. In this course, we’ll show you how you can use existing HTML, JavaScript and CSS skills and assets to build mobile apps using their simple model. We’ll also show you when you wouldn’t want to use PhoneGap and where it fits into most developers bag of tricks
I encourage you to check out Practical PhoneGap.
Jim Wilson (a.k.a. hedgehogjim) 
Java and Android SDK’s both are useful to develop unique and interesting Android apps for Android Development technology.
Can you explain about the iOS Native apps in brief..?
I totally agree with you that Java & the Android SDK is a great way to build Android apps (that’s what I use). iPhone on the other hand requires using Objective C and the iPhone SDK which some people find more difficult than Java and the Android SDK. And even if one find’s both equally usable, the two platforms required completely separate approaches which, in many cases, is nearly double the effort of targeting just one of the platforms.
The value of PhoneGap, as I understand it, is 2-fold. The first is that it allows people with web-based skills (HTML, CSS, JavaScript) to apply those existing skills to mobile apps. PhoneGap also makes it easier to target both Android & iPhone because it abstracts away many of the details of the underlying platform.
Thanks for your detail information. Now, I can completely understand about the iOS Native apps which you explain me.