Corporate Mission: It is a written declaration of an organization's core principle and focus which generally remains unaffected over time. Appropriately crafted mission statements (A) serve as filters to separate what is significant from what is not, (B) clearly state that markets will be served and how, and (C) communicate a logic of intended direction to the whole organization.
A mission is distinct from a vision in that the previous is the cause and the later is the consequence; a mission is somewhat to be accomplished while a vision is something to be followed for that accomplishment.