The platform behind this project is Apache Cordova, an open-source framework that enables web apps to be compiled much like native applications, allowing them access to native operating system functions and hardware sensors like the camera and accelerometer. Research In Motion (now Blackberry) also used a similarly customized version of Cordova to support native web apps on Blackberry 10. While this is the toolchain used to compile the code, it can also be paired with popular UI frameworks like jQuery for rapid development.
This opens up a great option for cross-platform development, where a single code base can run on several different operating systems. Web developers now have an easy path for porting their apps to mobile devices, even adding functionality that couldn't be accessed when their code was limited to a web browser. Unfortunately, we can probably expect a sharp increase in garbage apps from lazy developers and interfaces that don't fit in well with Android.
If you're interested in getting started with this framework, you'll want to read through the instructions for getting started. Android development requires version 4.4.2 or above of the Android SDK, but it can target any version of Android as far back as Ice Cream Sandwich. The minimum iOS SDK is not specified, but iOS 6 and above are supported. Of course, building for iOS must still be done on Mac OS and your apps must still pass Apple's requirements to enter their App Store. You can also check out several existing sample apps here. Keep in mind that this is still a developer preview, so there will probably be a few bugs to work out.