The Stars collected throughout the game are used to keep rank and place players on the Leaderboards.
Stars can be earned by building your Village items and by collecting new Cards. Village items reward one star per upgrade and Cards reward the number of stars shown at the top of each one.
When a player Attacks a Village and lands a direct hit on one of the items, it removes one star from the item as well as from the overall stars collected.
Please note that duplicate cards do not earn stars.