The symbol found on the flag for NATO (North Atlantic Treaty Organization) is the design of a four point white compass rose emblem, with four white lines radiating from the four cardinal directions (North, South, East and West). Adopted three years after the creation of the organization, it has been the flag of NATO since October 14, 1953. The dark blue color symbolizes the Atlantic Ocean, while the circle stands for unity among the member states. Also, the colors of the flag carry cultural, political, and regional meanings. The compass rose emblem symbolizes the direction towards the path of peace, the goal that each member state should seek.

More Info: en.wikipedia.org