Produced in Twig Snappers, Twigs are mainly used for constructing and upgrading buildings (Make sure to get a lot of twigs early on, because you will need them later). It is also used for Twig Missiles in the Catapult (less damage than Pebble Bombs but still good). The twig missile is mainly used for destroying high level buildings as it does concetrated damage on a small amount of buildings. You get more Twigs in battle!
You can buy Twigs with a certain amount of Shiny in the General Store (changes depending on the amount). Buying resources is not recommended since it is not very efficient or worth your Shiny.