The word "psilophytales" is a noun that refers to a group of very old plants that lived during a time called the Paleozoic era, which was millions of years ago. These plants were simple in structure and had a unique way of growing — they branched out in two directions, which is called "dichotomously branched." They are also known as some of the earliest types of vascular plants, meaning they had a system for transporting water and nutrients.
In more advanced contexts, you might discuss the ecological role of psilophytales in ancient ecosystems or compare them to other early plant groups.