Listening is receiving language through the ears. Listening involves identifying the sounds of speech and processing them into words and sentences. When we listen, we use our ears to receive individual sounds (letters, stress, rhythm and pauses) and we use our brain to convert these into messages that mean something to us.
Listening in any language requires focus and attention. It is a skill that some people need to work at harder than others. People who have difficulty concentrating are typically poor listeners. Listening in a second language requires even greater focus.
Like babies, we learn this skill by listening to people who already know how to speak the language. This may or may not include native speakers. For practice, you can listen to live or recorded voices. The most important thing is to listen to a variety of voices as often as you can.