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It notes the ship's primary weapon so the ship AI can use that weapon's range to judge it's preferred position in battle for the stance selected.

Setting the star in the design screen when you submit a design sets the default for all ships of that class, though you are free to change it in-battle for individual ships (though you'll have to make changes from the default every battle).
 
Ok thats what I thought they were for but I wasn't sure, but they don't always seem to work right because I have put the star on missiles and still the fleet moves to close range even though I set the stance to be at maximum range. (Bad for fleet)
 
Bad AI warmonger, the combat AI still needs a lot of work on boths sides yours and the AI players. Hopefully this will improve within the next couple of weeks as we get closer to the "release" of a functional 1.0 build.
 
Ok thats what I thought they were for but I wasn't sure, but they don't always seem to work right because I have put the star on missiles and still the fleet moves to close range even though I set the stance to be at maximum range. (Bad for fleet)

Standoff = maximum range for primary weapons
Close to Attack = medium range for primary weapons
Pursuit = Close range for primary weapons

So make sure you set your missile boats to Standoff as well as have the missiles selected as primary weapon.