Almost every credit decision reduces to one question. Not how much revenue you generate, and not how profitable you look, but whether the cash the business actually produces can cover what it owes with enough margin that a bad quarter does not become a default.
Coverage ratios are how a credit team measures that. They look objective, and the arithmetic is simple, but the inputs are where the real negotiation happens. Two people can run the same formula on the same business and land a full turn apart, entirely on what they allow into the numerator.
This is the map of that territory: what each ratio measures, where the numbers get argued over, and which test actually binds when several are running at once.