An annual plant is a plant that will live outdoors for one year.  Depending on the variety, the blooming season can be short lived (2 weeks to one month) or all summer long until cold weather sets in.  Some annuals are self seeding.  Some plants classified as "annuals" are actually "biennials", the latter meaning it will grow in one season and return after the following winter.  Pansies, Dianthus, Snapdragons, Dusty Miller are some examples.  Annuals are showy flowers and plants that will add instant color to your garden.