An electoral college is a group of people who are chosen to elect a candidate to a particular office (job). The electors usually have one vote each. Often each elector represents a particular organization or entity. Many times, though, the electors are simply important people whose wisdom would ideally make a better choice than a larger group of people. The electoral college can ignore the wishes of a general membership.
A similar concept existed in the former Holy Roman Empire, in which the Holy Roman Emperor was elected by the rulers of various provinces of the Empire, or their representatives. These rulers were referred to as Electors. For instance, King George III of Great Britain was also Duke and prince-elector of Brunswick-Lüneburg ("Hanover") and later became King of Hanover, though he never visited Hanover.