Worker is a hoodlum who is attempting to gain status in the family.
The worker is gradually brought into a family through a series of jobs, starting with small crimes, then be present at bigger crimes, then being a mission, then performing the crime.
It is not an official position in a Mafia but more of a shoe and higher ranks usually tell them "Know your place. Accept your place. Be a shoe. We are the foot, we tell you what to do." So workers must do their order or else no dessert for them.
Workers usually perform hard or simple task depends what a higher rank decides but do a lot of "thief work" like: stealing stolen goods in a truck and compliment your truck driver, threatening other family gangsters to earn some money and then "maybe" get a higher rank. They are called "slaves" because they are "a shoe", family business dealings are not discussed with them, it's only once they have worked their way up to Wise Guy status that they are given the chance to make their bones.