Short answers, pulled from the story.
Bark is the outermost layer of the stems and roots of woody plants such as trees, woody vines, and shrubs. It is a nontechnical term covering all the tissues outside the vascular cambium, and it consists of an inner bark and an outer bark.
The inner bark, in older stems, is living tissue that includes the innermost layer of the periderm. The outer bark is the dead tissue on the surface of the stem, including parts of the outermost periderm and the tissues outside it, and on trees it is also called the rhytidome.
The periderm is a secondary covering that forms on small woody stems and many non-woody plants. It is composed of cork or phellem, the cork cambium or phellogen, and the phelloderm, and it replaces the epidermis as a protective layer.
Removing a band of phloem all the way around the stem blocks the transport of photosynthetic products through the plant, and the plant usually dies quickly. This method is called girdling and is used as a forestry or horticultural technique.
Products made from bark include cork, cinnamon, quinine from the bark of Cinchona, and aspirin from the bark of willow trees. Bark also yields tannic acid from oak for tanning, bast fibers for rope, bark mulch, and bark bread made in Scandinavia from scots pine or birch.
Bark tissue makes up between 10 and 20 percent of the weight of woody vascular plants and consists of biopolymers, tannins, lignin, suberin, and polysaccharides. Up to 40 percent of bark tissue is lignin, which provides structural support by crosslinking polysaccharides such as cellulose.
Cork is the outermost layer of a woody stem, derived from the cork cambium, and is often confused with bark in everyday speech. Cork cell walls contain suberin, a waxy substance that protects the stem from water loss, insect invasion, and infection by bacteria and fungal spores.