What is Standard coupon, upfront payment?

A standard coupon is a fixed running premium, the same for all contracts of a class, which the market trades instead of a coupon negotiated for each trade. The upfront payment is the amount, in per cent of notional, that one party pays the other when the trade starts so that the contract with the standard coupon is fair at the market’s spread; the protection buyer pays it when the spread is above the coupon and receives it when below.