Entrapment is a law enforcement officer's fraudulent inducement of a person to commit a crime for the purpose of later charging the person with that crime. In other words, a person is entrapped if a law enforcement officer (or his/her agent) engaged in conduct
that would cause a normally law-abiding person to commit the crime. In a criminal trial, entrapment is an affirmative defense to such charges. (i.e., if the defendant can prove entrapment with a preponderance of the evidence standard, the prosecution will generally not be able to convict him.) When putting forward an entrapment defense, the defendant must generally prove that if he had not been forced or tricked by law enforcement into committing the crime for the purpose of prosecution, the crime would not have been committed. For example, if a former prostitute is picked up in a bar by an undercover police officer and they start what she believes is a legitimate relationship (she repeatedly refuses to take money when they engage in sexual relations), but one day she accepts his offer of money to help her pay her rent and the police officer then has her arrested for prostitution, she will probably be able to use an entrapment defense to avoid prosecution.
If you believe you were entrapped into committing a crime, consult with an experienced criminal defense attorney to learn about your rights, defenses, and any and all of your legal options.