What is the difference between a shallow copy and a deep copy of an object?

A shallow copy duplicates immediate properties of an object, meaning it creates a new object that has the same values for primitive properties as the original object. However, if the original object has references to nested objects, the shallow copy will not create new instances of those nested objects; instead, it will reference the same nested objects. This means that changes made to the nested objects in the copied instance will reflect in the original object because both refer to the same nested objects.

In contrast, a deep copy creates a new instance of the object and recursively copies all properties, including the nested objects, ensuring that no references to the original object's nested objects are preserved. Therefore, modifying a nested property in a deep copy will not affect the original object.

Thus, the definition of a shallow copy as the one that duplicates only the immediate properties captures the essence of how this type of copy operates in relation to the original object. It is important to grasp this distinction, especially when dealing with complex object structures in programming, as it affects how data is manipulated and maintained within the code.