Good Samaritan is a set of laws that is different in every state.
However, they are usually concerning medical attention. Like CPR. For example, I’m not certified in CPR, nor am I certified to give certain drug doses to save people’s lives. I plan to get certified as soon as I can, but that’s besides the point.
Because I am not certified, does not stop me from doing CPR. If someone went down and had no pulse, you damn well should know I’d be following my parents’ footsteps with a calm head and quickly doing CPR on the patient who needs it.
Say I end up breaking some of their ribs (which is normal, usually), but I do serious damage to their lungs, yet they survive through the attack and get to the hospital. Their family, nor they, can sue me for adding onto their hospital bill to fix their lungs. They cannot sue me at all for using CPR, for I was trying to save their life. Hence, “Good Samaritan”.