Concentration is the act of focussing. It is a narrowing of perspective.
Extraneous distractions are blocked out and the attention is directed towards a limited target.
Keeping your mind on what you are doing is excellent. It improves quality.
Sometimes, it is good to be distracted, to notice unexpected possibilities, to wander off in new directions.
However, there is a danger with distraction: the more distracted you become, the less competent you are.