What is the difference between Comparable and Comparator in Java?

Comparable is implemented by the class itself via compareTo(), defining one single 'natural' ordering (e.g., a Product sorting by its own ID); Comparator is a separate object implementing compare(a, b), letting you define multiple, external, interchangeable orderings for the same class (e.g., sort Products by price, then by name) without modifying the class itself.