Medals are won by secret agents if they succeed in secret missions. Letters and cards may come with your medal if you do other things.
In Mission 1, you will receive the Golden Puffles medal for terrific performance in locating and returning Aunt Arctic's two missing puffles. You will also receive a letter from Aunt Arctic if you give her the pictures of her puffles from the ice rink.
Note: I'll continue next time.