Concentration doesn’t just mean ‘the ability to study for a test’, or ‘the ability to stay focused on one thing for an extended period of time’.
No, concentration also involves choosing what it is that you’re concentrating on, as well as bringing yourself back to whatever it is you’d like to concentrate on after becoming distracted.
It (concentration) doesn’t have to be for a very long time either.
You can concentrate on something briefly.
Concentration is a skill that you can practice and develop, just like lifting weights.
Matt Fried 