`WeakSet` is a built-in object in JavaScript introduced with ECMAScript 2015 (ES6) that provides a collection for storing weakly held object references. It is similar to a `Set`, but there are a few key differences.

In a `WeakSet`, only objects can be added as values, and each object can occur only once in the set. The key distinction lies in the “weak” aspect – unlike a `Set`, a `WeakSet` does not prevent its elements from being garbage-collected if there are no other references to those objects in the program. This makes `WeakSet` useful for scenarios where you want to associate data with objects without preventing those objects from being cleaned up when they are no longer needed. `WeakSet` does not have iteration methods, size property, or clear method, and its primary operations are `add`, `has`, and `delete`. It is commonly used in scenarios where temporary associations between objects need to be established without creating memory retention issues, promoting more efficient memory management in certain use cases.