The App tests how quickly you can react to Audio & Visual Signals, There are two 45 second tests which gives you your average reaction times, you can then upload your test score and compare it to other users, you can see how well you fare against other users.
Audio test
basically soon as you hear a bleep sound you make a slight movement with your iPhone/iPad. You are given the reaction time and overall reaction time.
Visual Test
You click the corresponding colour based on the title, like audio test both reaction time and overall reaction time will be given.
after both tests have been completed You can Upload the test score and Compare Yourself to other users.