Growth ring
Rings happen because of the change in growth speed through winter, spring, summer and fall, so one ring usually marks the passage of one year in the life of the tree. Tree rings are more visible in places where the seasons change between hot and cold. Enough moisture and a long growing season result in a wide ring. A dry year may result in a very narrow ring. Trees from the same area will tend to grow the same pattern of rings. Cut all the way though a tree horizontally, like a stump, to find the growth rings.