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 bond is a debt investment in which an investor loans money to an entity (typically corporate or governmental) which borrows the funds for a defined period of time at a variable or fixed interest rate. Bonds are used by companies, municipalities, states and sovereign governments to raise money and finance a variety of projects and activities.
A letter of credit is a liability for the bank because it is an obligation to pay out money. On the other hand, a bank bond is essentially an insurance product, so it counts as an asset: If everything goes smoothly, the bank keeps its fee and does not need to pay the bondholder.