In badminton, with this mental term “concentration” is said, that thoughts must concern just the game when playing.
Other terms are “focus” and “attention”.

Not clear is on what exact is concentrated. It is a wills act that sometimes costs pains.
Often is just said or ordered, "Focus!", or "Concentrate!", sometimes applied with "on the play", when lack of attention is the case.

In the context of these explanations will “attention” be used, whereby an open mind is required to just perceive what all happens in the game. Relaxing is used therewith.
Attention is naturally present then and may be slightly switched to an aspect of the game, like the shuttle or positions, etcetera.
Perceiving the whole game stays necessary as long as the game takes.
When staying attentively, fantasy and thoughts will meanwhile help to play the right game.
When staying attentively, and perceiving then what all happens in the game, fantasy and thoughts do their work in the background. These are directly transformed into acting. So to say, Thinking is doing.
In fact, what stays, is perceiving and acting.