An entity which provides insurance is known as an insurer, insurance company, insurance carrier or underwriter. A person or entity who buys insurance is known as an insured or as a policyholder. The insurance transaction involves the insured assuming a guaranteed and known relatively small loss in the form of payment to the insurer in exchange for the insurer's promise to compensate the insured in the event of a covered loss. The loss may or may not be financial, but it must be reducible to financial terms, and usually involves something in which the insured has an insurable interest established by ownership, possession, or preexisting relationship.
The insured receives a contract, called the insurance policy, which details the conditions and circumstances under which the insurer will compensate the insured. The amount of money charged by the insurer to the insured for the coverage set forth in the insurance policy is called the premium. If the insured experiences a loss which is potentially covered by the insurance policy, the insured submits a claim to the insurer for processing by a claims adjuster. The insurer may hedge its own risk by taking out reinsurance, whereby another insurance company agrees to carry some of the risk, especially if the primary insurer deems the risk too large for it to carry.
Methods for transferring or distributing risk were practiced by Chinese and Babylonian traders as long ago as the 3rd and 2nd millennia BC, respectively. Chinese merchants travelling treacherous river rapids would redistribute their wares across many vessels to limit the loss due to any single vessel's capsizing. The Babylonians developed a system which was recorded in the famous Code of Hammurabi, c. 1750 BC, and practiced by early Mediterranean sailing merchants. If a merchant received a loan to fund his shipment, he would pay the lender an additional sum in exchange for the lender's guarantee to cancel the loan should the shipment be stolen, or lost at sea.
Circa 800 BC, the inhabitants of Rhodes created the 'general average'. This allowed groups of merchants to pay to insure their goods being shipped together. The collected premiums would be used to reimburse any merchant whose goods were jettisoned during transport, whether due to storm or sinkage.
Separate insurance contracts (i.e., insurance policies not bundled with loans or other kinds of contracts) were invented in Genoa in the 14th century, as were insurance pools backed by pledges of landed estates. The first known insurance contract dates from Genoa in 1347, and in the next century maritime insurance developed widely and premiums were intuitively varied with risks. These new insurance contracts allowed insurance to be separated from investment, a separation of roles that first proved useful in marine insurance.
Property insurance as we know it today can be traced to the Great Fire of London, which in 1666 devoured more than 13,000 houses. The devastating effects of the fire converted the development of insurance "from a matter of convenience into one of urgency, a change of opinion reflected in Sir Christopher Wren's inclusion of a site for 'the Insurance Office' in his new plan for London in 1667." A number of attempted fire insurance schemes came to nothing, but in 1681, economist Nicholas Barbon and eleven associates established the first fire insurance company, the "Insurance Office for Houses," at the back of the Royal Exchange to insure brick and frame homes. Initially, 5,000 homes were insured by his Insurance Office.