the.com/mother ship

means The main base, vessel, or headquarters from which smaller units, craft, or outposts operate and to which they return.

from A literal 20th-century naval and maritime term — the 'mother ship' was the larger vessel that carried, launched, and resupplied smaller boats, submarines, or aircraft, much as a mother tends to young that range outward from her. The phrase later drifted into sci-fi, where alien motherships hover above the fray sending out fighters, and into business jargon, where it now means head office, the place all the branch offices phone home to.