The purpose of a Comparator is to compare to objects, while an object implementing Comparable means that this object can be compared to another object of the same type. It's easier ot understand if you try to make a sample
Can you explain in more detail what exactly you don't understand about Comparable and Comparator? It's hard to help you if you ask your question in such a vague and general way - it means we have to guess what you're exactly not clear about.