The number of players on the pitch varies from tournament to tournament. In general, we are playing either 6 v 6 or 7 v 7 throughout the indoor season.
I like this formation because it provides balance on the field. In that balance, we have equal strength in attacking and defending.
Alternatively, we may use this formation when trying to protect a lead. This becomes more important if we need a win for points or to move on in an elimination finals format.