What is the purpose of the center circle?
The center circle is used to indicate the minimum distance the opposition team must keep at any kick-off point during the match. Only players who are on the team kicking off can enter the circle at this point.
The center circle along with the halfway line can also be used during a penalty shoot-out when all players must stay behind or within this area. The only players allowed outside this area are the two goalkeepers and the current penalty taker.