Tea is from one plant, in simple terms, while herbals are a wide variety, from many different plants.
Tea has caffeine. Almost no herbals do, with a few exceptions such as yerba mate (contains matteine), guarana, and cacao. Herbals are sometimes referred to as tisanes.
Tea becomes green, oolong and black by a process of oxidation. White tea is simply picked and dried, but a small amount of oxidation occurs naturally. Puerh is a fermented tea. Matcha is tea leaves ground to a fine powder.
While there is much more that could be said about both tea and herbals, this will give you a good foundation for beginning a long and wonderful tea and herbal journey.