A Juniper Berry is not a berry but a female seed cone. The cone has unusually fleshy and merged scales giving it a berry-like appearance. They are green when young and mature into a purple-black colour when about 18 months. Juniper berries used in distilling gin are fully grown, but immature green berries.
Juniper berries are the only spice which is derived from conifers. All juniper species produce berries, but some are too bitter to eat and some are toxic.