'Hear' is one of your five senses (hear,see, feel, smell, taste). Hearing is involuntary. 'Listen' is a conscious, voluntary action. Listen means to actively pay attention to an auditory stimulus. Hear is often used with 'can' . Can you speak up? I can't hear you very well. This apartment is really noisy. You can hear all the sounds from the street. Listen needs the preposition 'to' before its object. Listen! Listen to me! Listen to what the teacher is saying. I like listening to classical music. NB the difference between 'listen' and 'hear' is the same as the difference between 'look/watch' and 'see'.

I'll just add this song by Mike + The Mechanics: https://www.youtube.com/watch?v=gUdiQWxps5E (follow the lyrics and you'll see why) ;)