What is the nature and extent of slavery?
I hope you will clarify this question because it is not at all clear. Are you talking about the state of slavery in today's world? I will answer this as if that is what you are asking.
I would say that the nature of slavery today is not like it used to be. In the old days, you had people who were openly enslaved, working as servants for people or as laborers on their plantations. Nowadays, slavery is more usually hidden.
A typical slave these days is someone who has been brought illegally from a poor country to a rich country. The slave is often being enslaved as a way to repay the people who brought him or her (so it's sort of like indentured servitude). These slaves are often forced to work as prostitutes until they pay off the smugglers.