Homologous+and+Analogous+Structures

Homologous structures are structures with similar origins, but used for functions that are different from each other. An example of this would be the fins of a whale and the arms of a human.

Analogous structures are structures with similar functions, but have different origins. An example of this would be the wings of a bat and the wings of a bee. They are both used for flying, but have different origins.  

http://atheism.about.com/library/glossary/evolution/bldef_analogous.htm