It's a comparison of the current, Dalvik, runtime with its presumed successor, ART ("Android RunTime"), which first appeared with Android 4.4 "KitKat". They compare the systems in terms of battery life and performance and the like - see Meet ART, Part 2: Benchmarks - Performance Won't Blow You Away Today, But It Will Get Better
Basically, we're talking about the crucial Android middleware that runs your apps. And whereas Dalvik runs a Just-In-Time compiler, ART apparently uses an Ahead-of-Time compiler (AOT)...
Cody Toombs writes:
The numbers and the videos together paint a picture of where ART stands today. It will definitely make a difference, but its current incarnation just hasn't matured enough to deliver significant gains. Floating-point calculations and basic responsiveness are obviously reaping the benefits of the new runtime, but that's about it. There's little or no overall improvement for integer calculations, most regular code execution, or much of anything else. In fact, it looks like gamers would be better served by sticking to Dalvik, for now.