BTU, or British thermal unit, is the industry-standard used to measure the heating efficiency of furnaces. In addition to BTU ratings, furnace manufacturers might include a Manual J Load rating and a percentage of energy efficiency.
A debenture is a type of debt instrument that is not secured by physical assets or collateral. Debentures are backed only by the general creditworthiness and reputation of the issuer. Both corporations and governments frequently issue this type of bond to secure capital.
Thus a bond is a form of loan or IOU: the holder of the bond is the lender (creditor), the issuer of the bond is the borrower (debtor), and the coupon is the interest. Bonds provide the borrower with external funds to finance long-term investments, or, in the case of government bonds, to finance current expenditure.