mission statement

A written declaration of an organization's core purpose and focus that normally remains unchanged over time. 

Properly crafted mission statements 

(1) serve as filters to separate what is important from what is not, 

(2) clearly state which markets will be served and how, and 

(3) communicate a sense of intended direction to the entire organization.

A mission is different from a vision in that the former is the cause and the latter is the effect; 
a mission is something to be accomplished whereas a vision is something to be pursued for that accomplishment. 
Also called company mission, corporate mission, or corporate purpose.