Final answer:
The 'Echo' flag in maritime signal flags means the ship is altering its course to starboard. It is a part of the International Code of Signals used by ships to communicate on the water.
Step-by-step explanation:
In maritime signal flags, the flag Echo signifies I am altering my course to starboard. When the 'Echo' flag is hoisted on a ship, it is communicating a navigational maneuver to other vessels in the vicinity to help avoid collisions or misunderstandings on the water. This system of signaling is known as the International Code of Signals (ICS) and is used by ships to transmit important messages regarding their intentions, condition, or other vital information.