Great question! Perennials are plants where the above ground portion dies back at the end of every year but then regrows from the roots year after year. Over time the size of the plant will increase and most take three years to establish to maturity. If they ever get too large they can be dug up and split in half, or multiple portions, and replanted in another location. These aspects makes them cost effective over annuals, which are the type of plants that need to be purchased every spring because they do not survive the winter.
Take a look at my social media to see examples of many great perennials.