Botanists have developed quite a vocabulary of terms for all the parts of a plant, most of which a gardener will never encounter. There are, however, quite a few useful and descriptive words that gardeners have adopted simply because there aren't any other ones available. You'll encounter these fairly frequently as you learn more about the skill of creating gardens.
Annual plants (and perennials that sprout from the roots each spring) have soft stems, or shoots, which last no more than a year. In trees and shrubs, these stems harden into trunks and branches. The green layer between the bark and the wood inside--the layer that grows new tissue--is called the cambium. The tip of a branch is called the terminal bud; this is the point at which most new growth will occur.
Some stems become modified into runners that grow horizontally over or just under the ground, sometimes being leafy, sometimes root-like. Rhizomes are stems that grow underground, often becoming thickened with food stored for survival, and sometimes ending in tubers, like potatoes.
Leaves have a flat blade with veins that attach to a branch with a small stem called a petiole. The place where it attaches is called a node. There are usually one or more axillary buds at each node--small but noticeable buds that grow into new stems or leaves. The space between nodes is called an internode.
Most flowers have large, colorful petals with smaller green sepals beneath them. These surround the reproductive parts of the flower: the male stamen, with anthers at the top that hold pollen; and the female pistil, which includes a rounded ovule at the bottom.
Roots grow down from the surface of the soil, often becoming woody just as branches do. As they divide into smaller and smaller branches, they form single cell thick root hairs that are able to absorb water and nutrients. Taproots are major roots that grow straight downwards, often extending 5 or 6 feet or more into the soil. Adventitious roots form directly from the node of a stem or branch that has grown along the ground.