"Developing mobile applications used to mean that you had to write native code, for each individual device or operating system that your client required. However, these past few years the term Hybrid App Development has been conquering headlines, and for good reason."
Development frameworks such as Adobe's Cordova have made programmer's the world over happier. It's not that the code itself is easier, but rather that you can now write your software in just one language, and translate it into operating system-specific code. So write your software in PHP and Java, or whatever feels most natural to you, and then convert and compile your scripts into Android, iOS and other specific systems.
With heavyweights such as Adobe, Facebook and Instagram all investing in frameworks such as Xamarin, Ionic and lately Apple and Swift, this author foresees a bright future for this new breed of programming. You aren't even limited to making mobile applications, you can develop websites and any program you would want to run on MacOS or Windows even.
It is important to distinguish between Native and Hybrid apps, because the native development has a few things going for it even with the major advantages of the hybrid systems. Most importantly, if you develop your app natively, you will use the device's built-in hardware to software capabilities, and often achieve better performance than you would using hybrid apps, since they use webview to run the applications.
Okay, I'm interested, now show me some frameworks!
If you are about to develop an application for a client, you might wait with exploring these frameworks, they can take some time getting used to, but if you are just toying around, or developing a minor project for school, I can recommend getting your feet wet with one of these.
The framework best suited for you might not be the best one suited for someone else, it all depends on which languages you prefer to work with, and your level of expertise. Do your own research ahead of starting any project, and you will be rewarded accordingly!