Homologous structures have the same basic plan but are adapted for different function.
For example, the pentadactyl limb of vertebrates has the same arrangement of bones in a bat's wing, a human arm, a dolphins flipper and a mole's claw. Although the basic plan is the same (single bone, two parallel bones, a block of bones and five digits) the plan has been adapted for a range of purposes.
Analogous structures do the same job but have different origins, for example a moth's wing and an eagle's wing, or an ant's leg and a dog's leg.
