Perennials: Perennials are defined as living for several years. Any plant that lives for upwards of 2 years and produces soft or succulent stems which die down every year, the roots remaining alive and sending up fresh growth the following year, is commonly designated a Perennial.
In Horticultural, any plant that persists more than 2 years are all perennials, which would then also include trees, vines and shrubs, however, the word perennial is usually reserved for herbaceous perennials (plants which die down to the ground annually). Then the groups shrubs, sub-shrubs and vines are formed for the others.
Shrubs: A shrub is a perennial plant with many persistent woody stems usually freely branching from the base. If the woody part is confined to the lower portion of the plant while the upper shoots are soft, the term sub-shrub is applied.
Sub-shrub: A low-growing plant with woody stems-a small shrub. Also a plant classified as a perennial with a woody base but soft, herbaceous stems in its upper part.
Vines: A vine is a term that is used for any climbing plant. It is not a true horticultural description but is a useful category when searching for just the right plant to sprawl or climb. These plants twine or self-cling by means of a modified stem, root, leaf or leaf stalk using plants or other objects for support. They are ideal and useful for filling in, and adding height and structure on trees, through shrubs, on walls or arbors or as a groundcover.
*Always keep in mind that some overlap occurs between plant groups, annual to biennial to perennial to shrubs & grasses, and such; because of this that is why you may find some plants under a different groupings in books and catalogs.