Switching involves using a long switch, like a fishing rod, the end of which is swept quickly over the surface of the grass.
The main purpose of switching is to 1) remove excess water such as early morning dew and 2) wormcasts - small piles of earth which facilitate weed growth and create muddy lumps; and 3) any other small natural debris such as leaves.
It is an important part of caring and maintaining the lawns in good order so if in doubt ask yourself two questions .... does the grass look wet and can I see wormcasts? If the answer to either is yes, then PLEASE SWITCH before playing.