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There are three officially recognized forms of Human trafficking in the world today.

The first is sexual exploitation which involves a pimp selling an individual (often female between the ages of 12 and 14) to a "date" or "john" for sexual favors, including, but not limited to sexual intercourse. These sorts of arrangements commonly occur at hotels, large events, strip clubs, brothels and massage/nail parlours. 

The second is labor trafficking in which an employer or producer of some sort makes a promise of paid employment to someone who either doesn't currently live in the area or is in some form of debt to them. Once the individual gets the position the employer will withold wages because of the debt or isolate the person in less than ideal conditions because they can't survive without them for various reasons (language barriers between the victim and the community are a common issue and the main reason that victims cannot reach out to local law enforcement).

The final form of trafficking is the Illegal Organ Trade. Often individuals are tricked into giving up an organ to make themselves some quick money and are then never paid, however violent attacks resulting in forced organ removal have also occured. 

In the end the federal definition of human trafficking is:

"the recruitment, harboring, transportation, provision, or obtaining of a person for labor or services through the use of force, fraud, or coercion for the purpose of subjection to involuntary servitude, peonage, debt bondage, or slavery".

Therefore any crime under this definition could be called human trafficking.