Cross references are like pointers to other portions of scripture that talk about similar words or subjects. When we look up and read these cross references, they can help us to understand things a little better. Cross references are usually found in the margin of the Bible, however, not all Bibles have them.
Chain references are similar to cross references, but are designed to progress through scripture revealing verses that pertain to a given subject. These can be handy when you wish to study a given subject like 'forgiveness'. When you find each verse in the chain reference, you will find the reference to the next verse that is listed for that topic.