parts of the body that have been used a long time ago but not anymore

simuler function

similar in position, structure, and evolutionary origin but not necessarily in function.

if you see a bone mussel or tissue that is now useless

because they developed independently as adaptations to a common function—flying.

An example of homologous structures are the limbs of humans, cats. Regardless of whether it is an arm, leg these structures are built upon the same bone structure. Homologies are the result of divergent evolution.

any tail is absorbed during development. The coccyx currently serves as an anchor for muscles; that wasn't its original purpose, so that's why it's considered vestigial.

Analogous structures are similar structures in unrelated organisms. These structures are similar because they do the same job, not because they share common ancestry.

Homologous structures exist in organisms that have a common ancestor, so they are monophyletic. Analogous structures are found in organisms that do not have a common ancestor. Analogous structures always have similar or identical functions, while homologous structures are not always the case.

Though goose bumps are a reflex rather than a permanent anatomical structure, they are widely considered to be vestigial in humans. The pilomotor reflex, to give them one of their technical names, occurs when the tiny muscle at the base of a hair follicle contracts, pulling the hair upright

dolphins and sharks both have fins, even though they aren't related. Both species developed fins because of how (and where) they live.

wings of bats and birds. These structures are homologous in that they are in both cases modifications of the forelimb bone structure of early reptiles. But birds' wings differ from those of bats in the number of digits and in having feathers for flight while bats have none.