Story Coins are part of the way you will acquire new cards in the NFTStory.Cards ecosystem. You can get these coins on the open market or purchase a bag of coins that will have a random variety of Story Coins in them.
Once you have these coins you will either blend them to upgrade them (bronze to silver, silver to gold, etc), blend them to get a new card, or blend a combination of coins and cards to get a new card. These blends will give you the cards you need to access the next part of the story you wish to pursue.
To see the current blends or open your treasure bags visit: http://nftstory.cards/nefty