Those are two VERY different things. Sex work, in my opinion, should be legalised. It implies consent, and is no worse than a day labourer hiring out his muscles to haul bricks or dig holes or cover potholes in the road. After all, if people are allowed to use their bodies as commodities that use to work with, what IS the difference between a construction labourer, or a farm labourer, or a cleaning maid, or a prostitute? They all are, at the end of the day, willingly using their bodies to earn money.
Sex slavery, however, is totally different. It implies lack of consent, and also a lack of earnings, since slaves have no autonomy and no rights, not even to their own bodies. The work they do is not done with their consent. In fact, it would be more accurate to call them victims of repeated and continuous sexual abuse and rape.
The grey area between the two, however, happens because of the vast human trafficking network in India and elsewhere. Many times, a prostitute may appear to be willing, but in reality, she might be a sex slave who is putting on a act so that she doesn't get killed by the people who have forced her into this profession and who make profits off her body.
