what's the difference between "to hear" and "to listen"

I need to know the difference between "to hear" and "to listen". Could you explain it to me, please? I'm not a native English speaker.


In a comment, John Lawler wrote:

Hear and listen (to) are both active sense verbs, in this case the verbs for the sense of hearing. The difference between them is that listen is a volitional activity (you do it on purpose), while hear is a non-volitional activity (you can do it accidentally). The same distinction is what distinguishes the visual sense verbs look (at) (volitional) and see (non-volitional).