To hear something means to just take in sounds - hearing is one of the 5 senses, where as listening usually means to concentrate/understand/think about what is being heard. Hearing is a sense, listening is a thought process or skill. This is why on language tests we have "listening tests" rather than "hearing tests"!

Hearing is a passive process. Listening is an active process.

Hearing has some other meanings too! for example if you want to say something that you have some information about it and you had gotten some news you will say: I heard something .... But if you want to talk about your ability of understanding sounds or..etc you will use hearing but if you want to talk about the ability of understanding by your ears you will use listening. Like:" My hearing ability has been reduced since I got mp3 player and use handsfree of it." and "listen to your teacher while he/she is teaching" in the second example editing "hearing" instead of "listening" is not suitable for the sentence .

Example: A hearing test would describe how well your ears are able to take in sound. A listening test would describe how you are able to pay attention to and understand the sounds your ears are taking in.

Thanks a lot