Tree species refer to the different types of trees that exist in nature, each with unique characteristics such as size, shape, and leaf structure. They can be classified into two main categories: deciduous trees, which lose their leaves in the fall, and coniferous trees, which usually remain green year-round and produce cones. There are thousands of tree species worldwide, ranging from the towering redwood to the small bonsai. Each species plays a vital role in its ecosystem, providing habitats for wildlife, improving air quality, and contributing to the overall health of the environment.