Quote Originally Posted by Medved View Post
These verbs are usually described as "unidirectional" vs "bidirectional" verbs. As it follows from the names, they behave differently, the unidirectional ones (ехать, лететь, идти, плыть) refer to situations when you drive/ride/move by whatever means one way, and the bidirectional (ездить, летать, ходить, плавать) imply "there and back" sort of trips, like in Inego's sample sentences.
Хммм, я бы так не сказал.

Птицы летают, рыбы плавают. — о способностях
Птицы летят, рыбы плывут. — о конкретном действии

При чем тут "туда и обратно"?