A tracking link is used to navigate to a specific ad. 

1. To distinguish the same offer from different sources (for example between Facebook and twitter), you should use the source ID. 

2. To distinguish the same offer between two different placements of an offer on the same source, you can use different sub IDs with the same source ID.

Pro tip: Use these different Source IDs and Sub Ids to help you run reports in the reporting tab. For more about that click here