Farm Decorations are items used to decorate your farm. These items can be purchased from the Store's Farm section under the Farm Decorations category. Farm Decoration can be purchased for either gold or gems, won randomly from Mysterious Farm Decoration Boxes, or received from certain Surprise Chests.
Some decorations are only available at certain times of the year. Other decorations can only be purchased if you've reached a certain minumum level in your Farming skill.