How do a Set and a Map differ in terms of data structure?

A Set and a Map are two distinct data structures that serve different purposes, which is reflected in their properties regarding the storage of elements.

A Set is designed to hold unique elements, which means it automatically eliminates any duplicates. When you add an item to a Set, if that item already exists, it won't be added again, ensuring that all entries are unique. This characteristic makes Sets great for scenarios where you need to track distinct items without concern for their order or the number of times they appear.

In contrast, a Map is a key-value pair collection where each key must be unique, but the values associated with those keys can be duplicated. This means you can have multiple keys pointing to the same value, but no two keys can be the same. Maps are useful for associating unique identifiers (keys) with specific data (values), allowing efficient lookups based on those unique keys.

In summary, the correct answer emphasizes that a Set does not allow duplicates, distinguishing it from a Map, which allows values to be duplicated, thus clarifying the core difference in how these data structures manage their elements.