To understand Human Trafficking, think the ‘Action-Means-Purpose Model’ and its 3 elements; the what, the how, and the why. We already know the what, so let’s look at the 'how':
Force; (violence) physical abuse or assault, sexual abuse or assault, or confinement - If a victim is forced, that could look like kidnapping. It can look like beatings or rapes, or involve use of physical restraint.
Fraud; (lies) false promises of work/living conditions, withholding promised wages, or contract fraud - If a victim is defrauded, it could look like lies about job possibilities (particularly relevant for non-citizens); i.e. if you are promised wages without contract or formal agreement, you have no recourse for proving you were lied to.
Coercion; (threats) harm to self/others, debt bondage, psychological manipulation, or document confiscation - A victim who is coerced may be blackmailed into a position where they are living as a slave. This can look like threats against a victim’s family, blackmail of sensitive material, or against a victim’s livelihood (threat about abuse of legal processes). Remember, we don’t need to prove coercion if we are talking about a child, but for educational purposes, with children it is often threatening to harm a family member or even a pet. If it is a parent that is trafficking their child, it’s the threat of withdrawal of basic necessities or even as simple as the threat of withholding love.
The 'why'. For now, let's leave it at the number one reason - greed. Per the International Labor Organization, human trafficking is the second largest and THE fastest growing criminal enterprise in the world at over $150 Billion dollars a year.