A mission statement is much more imbedded into non-profit organisations, than it will be for for-profit organisations, as the mission will be the entire justification for existence.

A mission statement should be an explanation of why the organisation exists. It is important that a mission statement expresses the core reason for an organisation to exist: It's purpose!

A mission should be able to drive the organisation forward and be the basis for the strategic plan. It is often confused with vision (see below).

To explain the distinction, the mission is why the organisation exists while vision is what you want to end up being.

Having a well-written and well-expressed mission statement will be able to inspire employees and volunteers. It may also work as a powerful tool when working with stakeholders and become a branding instrument for the organisation.

A great emphasis must, therefore, be placed in developing the mission statement, in such a way that it becomes more than a slogan.

Such development process will in some cases take month and not days. 

If a mission statement is to be effective, it much is a short, memorable and appropriate for a variety of organisational stakeholders including, for example, employees, funding sources, served constituencies and the board of trustees.

By formulating what the mission of the organisation is, a mission statement will also help setting up boundaries on the organisations activities.