In evolutionary biology, the term homologous structures pertain to the structures in different species with a common ancestor or developmental origin. Homologous structures may not necessarily perform the same function. For instance, the forelimbs of humans and bats are homologous structures. Although they are used differently, the basic skeletal structure is the same and they are derived from the same embryonic origin. Their similarity in this regard could indicate a likely evolution from a common ancestor.
In comparison, the structures showing similar function but evolve separately are called analogous structures. These structures from different species do not share a common ancestor. For example, the fins of fish and flippers of whales (mammals) are analogous structures. These animals use them for swimming. However, they are evolutionary not related in a way that they do not share a common ancestor.
The analogous structures may be dissimilar with regard to anatomy whereas the homologous structures may show similar anatomical features. In terms of development pattern, homologous structures show similar pattern whereas analogous structures do not.