Let's use YNAB as an example. YNAB wants to issue bonds, to borrow some money, to buy an office building (we would never borrow money in real life, to be honest). So we go to the bond buyers and say, "Hey, if you'll each lend us $1,000 we promise to pay you 7% interest." We issue 100 bonds, we have 100 bond buyers, and those bond buyers will all be paid 7% interest. That interest is called the coupon rate. YNAB gets $100,000 total (100 bond buyers * $1000 bond value), and each buyer can expect $70 of interest payments (7% * 1,000) each year.
