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.
Bonds and stocks are both securities, but the major difference between the two is that (capital) stockholders have an equity stake in a company (i.e., they are owners), whereas bondholders have a creditor stake in the company (i.e., they are lenders). Being a creditor, bondholders have priority over stockholders.