Plants are perennials if they live longer than two years; they may be short lived perennials or long lived perennials.
This covers a wide range of plants and species, as you can imagine. Trees, shrubs, some herbaceous plants, some aquatic plants, bulbs, corms and tubers are all perennials. They may be evergreen or deciduous perennials; woody or herbaceous (see below).
Generally speaking a short lived perennial will survive for between two and ten years. Long lived perennials can live to many hundreds of years, for example many tree species such as Oak. The oldest perennial plants are woody perennials.
Perennials may die back over winter or may maintain an above ground growth of leaf or stem all year.
A few examples of perennials –
Short lived deciduous woody perennials – Rose
Long lived deciduous woody perennials – Oak
Short lived evergreen woody perennials – Lavender
Long lived evergreen woody perennials – Metasequoia (Dawn Redwood)