If you concentrate on something, or concentrate your mind on it, you give all your attention to it.

If something is concentrated in an area, it is all there rather than being spread around.

Concentrate is a liquid or substance from which water has been removed in order to make it stronger, or to make it easier to store.

If you say that an unpleasant fact or situation concentrates someone's mind, you mean that it makes them think clearly, because they are aware of the serious consequences if they do not.