The Catechism in Questions & Answers

471. What is an appointment?

An appointment is the assignment of a firmly defined task. The appointment can be limited in terms of duration and location.
In association with a spiritual ministry, the term “appointment” is understood as the assignment to the task of congregational rector, district rector, District Apostle Helper, or Chief Apostle Helper. Such an appointment is not to be equated with an ordination. It is not bound to the duration of one’s ministerial activity, but can end before this activity ends. At the latest, it comes to an end when the minister retires.
In order to fulfil the various tasks within the congregations and districts, special mandates are issued to both brothers and sisters, independent of a spiritual ministry.