A phylogenetic tree is a diagram that represents the evolutionary relationships among various species or groups. It illustrates how different organisms are related through common ancestors, showing the branching patterns of evolution over time. Each branch point, or node, indicates a divergence where a single lineage splits into two or more lineages. These trees are constructed using data from various sources, such as genetic information, morphology, and fossil records. By analyzing these relationships, scientists can better understand the history of life on Earth and the processes that drive evolution, including natural selection and genetic drift.