Where they are allowed to score from in soccer?

Answer 1

Position does not matter when considering whether a goal was scored. All that matters is the situation surrounding the event. For example, the forwards and strikers of a team have just as much right and ability to score a goal as do the defenders and the goalkeeper. The position of the shooter does not matter.

The "situations" mentioned above that could prevent a goal consist mostly of technicalities in the Laws of the Game. The ball must be in play for a goal to be scored (duh), and it cannot be scored directly from an indirect free kick or a throw-in.