When the ball is in possession of the other team and it gets past the offense on your tem it is the defenders job to control it and pass it or clear it out of the area so you dont get scored on. You are defending the goal or goal. Hense, Defender.
he defends the goal without using his hands , this prevents one on one attacks by the opposing team, one of the most important roles on the pitch.
A back is a defender.
Yes, if you are a defender.
Pressure of the defender
a defender that is on the right side
John Terry of Chelsea and England.
goalie, defender, midfielder, forward
Today it is the Brazilian Danny Alaves.
Defender or Midfielder
The defender usually depends on the sport. In soccer (football) the defender is the one that protects the goal. I don't know much about football (American Football)