Topic or Fork
The cross reference dialog shows the targets both as part of the publication (fork) and outside the publication tree (topic or subpublication). When you insert a cross-reference in topics, you can link to either a topic or a fork. It is important that you understand the difference, as it will produce different results.
Tip
For more details, see Add Cross-Reference to a Topic and Add a Cross-Reference to an Element in a Specific Fork.