The sexual component need not be sexual intercourse or even physical touching. It could be any form of unwanted sexual activity, such as exposing ones private body parts, posing for sexually suggestive photos, participating in phone sex or submitting to inappropriate touching.
As for the corruption element, the perpetrator must be a person in authority who abuses that authority by indulging in the activity of demanding or accepting sexual favors in exchange for the exercise of that authority. In other words sextortion is a form of corruption in which sex and not money is the currency for the bribe.
Not all sexually abusive, exploitative, discriminatory or criminal conduct constitutes of sextortion.
Sextortion requires that the abuser have some form of executive authority over the victim. Where that authority is lacking, the sexual abuse is not sextortion
Sextortion also requires an exchange or quid pro quo — a benefit in exchange for a sexual favor. Where that exchange is missing, the sexually discriminatory conduct is not sextortion:
Info courtesy of The Sextortion Toolkit by Tanzania Women Judges Association