What are the key differences between a halfback, fullback, and running back in football, and how do their roles on the field vary?

In football, the key differences between a halfback, fullback, and running back lie in their positioning and roles on the field. A halfback typically lines up behind the quarterback and is known for their speed and agility, often used for running plays and catching passes. A fullback lines up closer to the line of scrimmage and is usually a bigger, more physical player, often used for blocking and short-yardage runs. A running back is a general term that encompasses both halfbacks and fullbacks, referring to any player primarily responsible for carrying the ball. Each position has specific responsibilities based on their skill set and positioning on the field.