Listening

Listening is not quite the same thing as hearing. Hearing is a biological process that can be scientifically explained, but listening is a psychological process of what happens to sounds as we interpret and use them. It is a cognitive activity.
In psychology, speech is part of pragmatics, a field which deals with signs and their interpretation. The signs in question are called "speech acts".
To listen means to try and understand what has been said. Listening is often one side of a conversation. Asking questions helps one understand what has been said. A subject can be better understood by asking the correct questions.
Listening differs from obeying. Parents often say to a disobedient child that he "didn't listen to me", meaning, he heard but didn't do as was suggested.
Listening also applies to sounds, not just language. It is "active" hearing. We hear a sound, and know what it means. This applies to animals as well. Cats list in the long grass for the little sounds that mice make. So perhaps a better description of listening is "deliberate hearing to get the meaning of sounds".