A more thorough explanation:

A defense is a way of protecting oneself from being held responsible for something. In the legal system, a defendant can use defenses to avoid or reduce their liability. A defense can either argue that the plaintiff or prosecutor has not provided enough evidence to support their claim, or it can acknowledge the claim but provide additional reasons why the defendant should not be held responsible.

• Failure to state a claim: If someone sues you for something, but they haven't provided enough evidence to support their claim, you can use this defense to argue that their case should be dismissed.
• Justification: If you were defending yourself or someone else when you committed an act that would normally be considered illegal, you can use this defense to argue that you were justified in your actions.
• Excuse: If you committed an act that would normally be considered illegal, but you had a good reason for doing so (such as being forced to do it by someone else), you can use this defense to argue that you should not be held responsible.

These examples illustrate how a defense can be used to protect oneself from legal liability. By using a defense, a defendant can argue that they should not be held responsible for something, either because the plaintiff or prosecutor has not provided enough evidence to support their claim, or because the defendant had a good reason for their actions.