Duress means any kind of threat or coercion that is used to force a person to enter into a contract or to do something against their wishes. Initially, there was only actual or violence that an individual was threatened for but now over a period of time, the doctrine has evolved to include duress of goods, duress by public officials and economic duress.  

The court protects those who have been forced to do anything that they did not want to do and is illegal in the eyes of law. No one should be forced to do anything; it should be voluntary in nature. When a contract is entered under coercion or not entered with one’s own wishes then the contract is considered as void ab initio. (not valid from the beginning)

For example: When a convict is questioned by the police, the police forces the convict to give a confession, it is under duress that this confession is given.