If you want the dictionary definition, just double click on any word.

To hear is a verb that means to receive or become aware of a sound using your ears. You don't have to make an effort in order to just hear something.

For example:-

She heard a noise outside.

Can you hear me?

To listen is a verb that means to give attention to someone or something in order to hear them clearly, so you make an effort in order to hear something and make sense of it.

For example:-

She listened to the noise and realised it was only a cat.

Are you listening?

Note! In some circumstances we use hear when we listen to someone or something attentively or officially.

For example:-

I heard a really interesting speech on the radio this morning.
These people need to be heard.