Church steeples are fashioned after military watchtowers starting AD 600. It appears that lots of OPC churches are structured with a steeple. Steeples are usually enclosure (belfry) for bells, a fashion adapted by Islam's minarets. A steeple could contain a lantern section between the spire and belfry.
Some churches have little or big cross on the spire (sharp pointy top part) of the steeple. The Mormons usually place a stature of their angel Moroni on it.
It's mainly a symbolic display of heaven pointing significance after the tradition of European and mainly British church architecture custom.
The OPC churches call what others refer to clergy house as manse. More commonly known as rectory elsewhere.