Football setpieces formation

I have been watching foot ball for 3 years. Its quite embarrasing i dont know how they mark themselves in set pieces. I just cant understand it. Any one please explain it? Next what is the sweeper in football?
Answer #1
Sweeper is a defender who is mainly behind the defenders and literally acts as a “sweeper”
Defender Defender Defender Defender
_____________Sweeper_______________
Set pieces:
http://en.wikipedia.org/wiki/Set_piece_%28football%29