Basic questions about Issue tracker and github repo of a project for development purpose

Application Name: Github Repositories and Issue tracker

Question: every project have 2 github repos one is project module and other sometime distro , client etc why is that so ?

And If I take a issue of a project which one should I fork?

And One more thing Can I determine which repository should I fork through ticket id or project key? Is github repo link available anywhere on project issue tracker site(example on this

sorry If it is irrelevant to Ask Openmrs but I really need to know these

have you looked at this