A widespread activity in religions of the proselytising kind comprises sending "missions" to convert and support new adherents. Some churches reflect the primacy of mission work in their structure and nomenclature. The term missionary stems from the proselytising sense of "mission". (see for instance: California mission).
The study of missions, particularly Christian missions, is missiology.
In military parlance, armed forces carry out missions as designated tasks. They obey with no necessary requirement for belief in the mission -- though such belief might lift morale.
Analogously to the religious use, some businesses see and label their marketing practices as "missions". Other businesses may simply subscribe to mission statements as credos.
The Mission is a 1986 film set in a Christian mission.