Human trafficking is the movement of people by deception, coercion or violence, in order to exploit them. It involves 3 elements:

What is done: recruiting, transporting, harbouring and receiving people

How it is done: using threats or the use of force, coercion, abduction, fraud or deception, abuse of power, payment etc.

Why it is done: in order to exploit people: Including sexual exploitation, forced labour, domestic servitude, other forms of slavery, removal of organs, controlling people so that they will perform criminal acts etc.

This is the internationally recognised definition of human trafficking:  

‘Trafficking in persons shall mean the recruitment, transportation, transfer, harbouring 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 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 of another person, for the purpose of exploitation. Exploitation shall include, at a minimum, the exploitation of the prostitution of others or other forms of sexual exploitation, forced labour or services, slavery or practices similar to slavery, servitude or removal of organs.’