From Chapter 14 ("Mindfulness versus Concentration") of Mindfulness in Plain English by Bhante Henepola Gunaratana:

Mindfulness is a broader and larger function than concentration. It is an all-encompassing function. Concentration is exclusive. It settles down on one item and ignores everything else. Mindfulness is inclusive. It stands back from the focus of attention and watches with a broad focus, quick to notice any change that occurs. If you have focused the mind on a stone, concentration will see only the stone. Mindfulness stands back from this process, aware of the stone, aware of the concentration focusing on the stone, aware of the intensity of that focus and instantly aware of the shift of attention when concentration is distracted. It is mindfulness which notices the distraction which has occurred, and it is mindfulness which redirects the attention to the stone. Mindfulness is more difficult to cultivate than concentration because it is a deeper-reaching function. Concentration is merely focusing of the mind, rather like a laser beam. It has the power to burn its way deep into the mind and illuminate what is there. But it does not understand what it sees. Mindfulness can examine the mechanics of selfishness and understand what it sees. Mindfulness can pierce the mystery of suffering and the mechanism of discomfort. Mindfulness can make you free.

^z - 2016-08-19