Credit vs Debt Markets

Just curious if there is any difference between the credit and debt markets? I know there are positions at banks for DCM, but then there are also credit research analysts, so I am just confused as to any discrepancy between the two?

Also, would anyone be willing to share their book/reading recommendations to get a good understanding of the credit markets and credit analysis? Especially someone who works in credit research or at a credit fund?

Thanks for your help, it is always much appreciated.