There is no duty to retreat inside one's home or place of business. Outside of those locations there is a duty to retreat if it can be done in "complete safety.". Deadly force may only be used if the person believes it necessary and the attacker has made threats of bodily harm, kidnapping, rape, or murder.
Castle Laws are laws that address the use of force when defending one's self inside their home, or on their property. Some states expand this to vehicles, and the person's place of work. Castle Laws generally include: the places where this law applies, the requirements fro use of deadly force, if there is a duty to retreat, the amount of force that maybe used in defending one's self or others. These vary widely from state to state.