Credit Spread

Credit spreads compare how much an investor could make on a Treasury security (government) versus some other debt security that’s not issued by the government.

Since the government doesn’t back the other securities, they are obviously a bit riskier (because there's a better chance they'll default, i.e. you won’t get paid) and have higher interest rates to make up for the risk.

Yeah...it's the whole "greater the risk, greater the reward" shtick.