Homology refers to the similarity in structure or function between different species due to shared ancestry. For example, the forelimbs of humans, whales, and bats have different functions but share a similar bone structure, indicating that these species evolved from a common ancestor. In biology, homology is important for understanding evolutionary relationships and can be identified through comparative anatomy, genetics, and embryology. It helps scientists classify organisms and trace the evolutionary history of traits, providing insights into how species adapt to their environments over time.