What is the difference between a deep copy and a shallow copy in programming?

A shallow copy creates a new container object but copies references to the objects inside, so nested objects are shared between the original and the copy. A deep copy recursively copies all nested objects, producing a completely independent structure. Shallow copies are faster and use less memory, but changes to mutable nested objects affect both copies. Deep copies are slower and use more memory, but they guarantee that modifications to the copy do not affect the original. For example, in Python, list.copy() or dict.copy() perform shallow copies, while copy.deepcopy() performs a deep copy. In Java, clone() typically performs a shallow copy unless overridden to clone nested objects. Understanding the difference is crucial when you need to avoid unintended side effects in data manipulation.