A more thorough explanation:

Personal defense is a type of defense used by a defendant in a legal case. It is a reason given by the defendant as to why the plaintiff or prosecutor does not have a valid case against them. There are different types of personal defenses, including:

• Affirmative defense: This is when a defendant asserts facts and arguments that, if true, will defeat the plaintiff's or prosecution's claim, even if all the allegations in the complaint are true. Examples of affirmative defenses are duress and self-defense.
• Real defense: This is a type of defense that is good against any possible claimant, so that the maker or drawer of a negotiable instrument can raise it even against a holder in due course. Examples of real defenses are fraud in the factum and discharge in bankruptcy.
• Personal defense: This is an ordinary defense in a contract action that the maker or drawer of a negotiable instrument is precluded from raising against a person who has the rights of a holder in due course. Examples of personal defenses are failure of consideration and nonperformance of a condition.

For example, if a person is accused of assault, they may use self-defense as a personal defense. They would argue that they acted in self-defense and therefore should not be held liable for the assault. This is an affirmative defense because they are asserting facts and arguments that, if true, will defeat the prosecution's claim.