Plants have one objective in life and that is to reproduce.
Reproduction is mostly done by seeding (spore in ferns) but can be also achieved through division, suckering, cloning, producing bulblets or pups. The desire to reproduce is their strongest attribute which is one that can make gardening very difficult at times. (weeds, suckers, oxalis).
There are two basic forms of plants, one is called annuals because they germinate, grow, flower, seed and then die. The other type are perennials which live for a number of seasons or in the case of some trees thousands of years. There are inbetweens such as bi-annuals which for our purpose here we will not worry about them.
Perennials are fairly straight forward, they live, they flower, they produce seeds, they may produce off sets, suckers (new plants from their root system) all while they live for more than one season. They can have their foliage removed and survive to generate more foliage unlike an annual plant which if their foliage is removed the root system dies.