A flagship is a vessel used by the commanding officer of a group of naval ships, reflecting the custom of its commander, characteristically a flag officer, flying a distinguishing flag. Used more loosely, it is the lead ship in a fleet of vessels, typically the first, largest, fastest, most heavily armed, or best known.
Over the years, the term "flagship" has been borrowed in metaphorical form by industries such as broadcasting, automobiles, cell phones, education, national airlines, breweries and retailing to refer to their highest profile or most expensive products and locations.
In common naval use, the term flagship is fundamentally a temporary designation; the flagship is wherever the admiral's flag is being flown. However, admirals have always needed additional facilities; a meeting room large enough to hold all the captains of the fleet, and a place for the admiral's staff to make plans and draw up orders.