Lightweight technology uses native code but renders the widgets itself instead of using native OS widgets. This is an old idea dating back to the days of smalltalk and was used on the desktop in frameworks such as Swing, QT, Flash etc.
In the mobile space the leading solutions in this field are Adobe Air, Codename One, Corona & QT.
Specs
Pros
Pro Write once, run anywhere
The portability of this solution often exceeds even HTML5 since it isn't limited by browser fragmentation.
Pro Native performance
Solutions often use low level graphics API's optimized for native games to produce the performance level of games while compiling the application to native.
Pro Deep customization and control
These solutions usually allow the developers to customize every aspect of the app to the finest details since everything is rendered by the solution
Pro Doesn't depend on OS whims
OS providers often change widget themes and behaviors on whims causing incompatibility and breaks in design/code. This isn't as much of a problem in such solutions.
Pro Ability to access native functionality
Solutions in this space can still call native code directly and sometimes even embed native widgets in place
