In Plantera you build your own garden and watch it grow with new plants, bushes trees and animals.
As you play and expand your garden you will attract helpers, round blue creatures that will help you pick up things and harvest your plants.
If you want you can pluck trees and harvest plants yourself, or let your helpers do the work for you while you watch or build and invest in new plants. The helpers will even continue to work while you are not playing the game, and some new gold should always be waiting for you on your return!
It is good to keep your eyes open though as sometimes some mean critters will invade your garden. Hunt them out yourself or invest in a guard dog to keep the order.
Go up in level to unlock new plants, bushes, trees and animals and continue to expand and improve your garden!