What does int, jit, fast, and portable mean in build.prop's dalvik.vm.execution-mode?

There are many build.prop tweaks on the internet, and some says dalvik.vm.execution-mode should be int:jit, and some says it should be fast:jit or even in a reversed order as jit:fast for performance. What is the difference between int and fast, and does the order matter (before and after the colon)? My phone is running Android 4.4.2 KitKat. Edit: Just a note, ART is not supported in my device (Samsung Galaxy Note 2), even if I install the dex2oat program and libart.so, it won't work.