Phylogenetic trees are constructed by comparing the similarities of biological sequences (such as DNA, RNA or protein sequences) to reveal the evolutionary relationships of different species or genes. It represents the genetic relationship and common ancestor between different species or genes in a branching structure. The construction of phylogenetic trees uses multiple sequence alignments and evolutionary models to help researchers understand the evolutionary history of organisms, population differentiation, and the origin and evolution of gene families. This has important implications for studying biodiversity, evolutionary biology and taxonomy.