In most Protestant churches, a minister is a member of the ordained clergy who leads a congregation; such a person may also be called a pastor, preacher, or elder. In many churches, ministers are required to be seminary trained although some churches allow laymen to preach. Compare with priest. In Catholic churches, not only ordained deacons, priests and bishops, are ministers, but there are also lay ministers, including lectors who read scriptural passages to the congregation, altar servers, and extraordinary ministers of communion.
A minister is a politician who heads a government ministry or department (e.g. education, finance, health, state, war etc...). Senior ministers are members of the cabinet, usually led by a prime minister or president.
Until the late 20th Century, ambassadors were also called ministers, ie: "Minister for Cuba" or "Minister for France."
A few ministers:
Lists of ministers