Originally the ambon was an elevated platform, somewhat variable in location within the church (but typically found toward the center of the nave, or somewhat forward from there), where the scriptures were read during the Divine Liturgy.
In the Russian Orthodox Church, during Hierarchical services, the bishop will stand upon a raised platform (kafedra) in the center of the nave like the bimah of old.
During the Rite of the Churching of Women, the newborn infant is taken by the priest up onto the ambon (provided the child has been baptized by this time—otherwise, this ceremony will wait until after the baptism).
In some Greek Orthodox parishes, there is an ambo to the side (usually the Liturgical North, opposite the Bishop's throne) of the Iconostasis.
In ancient times, there was a large collection of Prayers Before the Ambon, written for the different Feast Days of the church year and for those occasional services (Weddings, Funerals, etc.)