Junit testing, which type of methods and class should I test (OOP Java)

I have a person class, which has basic fields such as name, age, address etc. I haven't used junit testing that much, and was wondering what types of methods shall I test? I heard you should only test accessor methods or methods that returns a object/variable, is this true?

I also heard junit test is used to test classes such as Person, Animal, Cars etc.. What are these types of classes called, I know there is an terminology for it but forgot it atm