There are several professional level clubs, or leagues, found all around the globe. From Northern America to Africa to the most popular club in Europe. Within these clubs the regulations become a more enforced, but the basics remain. The teams are to be made up of eleven players on the field (not counting substitution players on the sidelines). For the most part, the field of play is a rectangle measuring 100 by 75 meters, and is not contained by walls. Players are free to move the ball in any direction on the field, thus allowing for unlimited passing and playmaking potential. The best teams are the ones that can effectively utilize each other when possessing the ball near the opponent's goal. Knowing where teammates are and which ones are not being defended against by the other team is vital when making an attempt on the goal. But there is a single player in the way of the goal-making attempt who has the ability to utilize their hands; the goalkeeper.
This goalie's job is to stay in the area of the goal and defend it using any body part at all, the goalie is the one player free to use their hands while on the field. Other than the goalie, there are no preset positions that the players must fill according to the rule book. But common positions have evolved over the years. Positions that call for players to stay back near their goal and assist (without hands) the goalie to positions that place players right up front constantly trying for the opponents goal.
For the most part soccer is a very low scoring game as these goalies are very good at what they do, not to mention the ball-stealing abilities of the defending team. A game ending with more than 5 goals in considered a bunch, while games with a score of 1 to 2 are more the norm.