Difference between Manage Job Offers vs Pending Workers

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We are trying to understand the difference usage between these two actions. We are able to convert from Pending Workers, then what is the usage of manage job offers?

Also, we have seen weird behavior like when I change the status to "Return to Manual Processing" and I go to Pending Worker and convert them, then I go back to Manage job offers and for the same candidate I see an option for Add Pending Worker and it creates another record. 

Thank you!