retain vs assign vs strong vs weak... vs whatever else there is?! D:

That stuff relates to memory management. atomic and nonatomic have to do with multithreading. atomic makes it so that the whole value is read at once. nonatomic does not guarantee that you will get the entire value back. retain is the old version of strong. You're telling the system to keep that property around until you let it go (in the case of retain) or the system determines it no longer needs it (in the case of strong). The rule of thumb is that if you have an object that relies on another object to exist you should make that property/object weak. For instance UI elements are usually weak because if you no longer have an instance of UIView or UIViewController that they're attached to that probably means you don't need them anymore.