Job enlargement is doing different tasks and not just the same thing all the time. It may involve taking on more duties and adds variety to a person's job. Horizontal loading is often used which is giving people more jobs to do that require the same level of skill.
Job rotation is the movement between different jobs. One day a person may be working in one part of the factory and the next day they may work in a different part. This avoids the employee becoming bored as with job rotation they are doing different jobs all the time and learning new skills. Multi skilling is when people have many skills so they are able to carry out many different jobs. Multi skilling benefits the employer as if they are short of staff in one area, they can move people across.