The Palermo Protocol defines trafficking in persons as: the recruitment, transportation, transfer, harboring or receipt of persons, by means of the threat or use of force or other forms of coercion, of abduction, of fraud, of deception, of the abuse of power or of a position of vulnerability or of the giving or receiving of payments or benefits to achieve the consent of a person having control over another person, for the purpose of exploitation.

And what is considered exploitation?

According to the Palermo Protocol. Exploitation shall include, at a minimum, the exploitation of the prostitution of others or other forms of sexual exploitation, forced labor or services, slavery or practices similar to slavery, servitude or the removal of organs.

The United Nations Convention against Transnational Organized Crime (2000) is supplemented by three Protocols:

• Against the Smuggling of Migrants.
• To prevent, suppress and punish trafficking in persons, especially women and children (Palermo Protocol).
• Against the illicit manufacturing of and trafficking in firearms. Mexico signed in 2002 and entered into force in 2003.

Human trafficking is a complex issue, however, 4 common stages have been identified: recruitment, isolation and subjugation, exploitation and exit. You can read more here.