Simply put, extensive listening is listening to a lot of comprehensible and enjoyable content. This means the listening materials should be fairly easy to understand (although it is OK if you don't understand 100%). Does this mean you listen to TED talks or the TV show 'Friends' all the time? Maybe, but only if it is not frustrating to listen to. If it's frustrating because you can't understand what they're saying or the content is boring or too technical, then the material is not extensive listening.
An important point that was mentioned in the previous paragraph is listening to a lot of content. If you listen to a language only once in a while, then you won't gain enough practice. It is suggested that you practice your language listening skills as often as you can with easy listening content. This could mean that you can only listen to a 10 minute podcast once a week, but maybe you have more time to listen than just once a week.
When you listen, don't focus too much on the vocabulary or grammar. What's important is that you understand the content.
How can Extensive Listening help me?
Extensive listening may help you improve comprehension (Kim, 2004), increase fluency, and get you comfortable with people's speaking speed, intonation, and way of taking (Renandya & Farrell, 2011).
How do I find Extensive listening materials?
First, check out this website page. It provides a lot of resources and more information on extensive listening. Some places you can look for listening materials outside of academic sites and materials are audiobooks, podcasts, radio shows, news, and YouTube. Keep in mind that all of these sources are not made for second/foreign language learners, so the material may not be an appropriate level.
One guaranteed place to find extensive listening material is through the Play It by Ear podcast that is hosted on this website! Check it out and see if it fits your level!
Connecting Extensive Listening and Extensive Reading
Although not proven by anyone, it is believed extensive reading (ER) came before extensive listening (EL) in regards to research and practice. Many people compare extensive listening and reading only seeing their similarities. Indeed, there are similarities between the two. Like ER, EL has a goal of increasing fluency and general comprehension. However, there are some differences between the two. In ER, a reader can spend as much time as they need on each word/sentence/paragraph, but in EL the listener only has as much time as the speaker allows. This means it is even more important that the listening materials are not too difficult. However, many researchers and teachers believe that the principles behind ER and EL are very similar, so research in EL often relies on ER research as well.
Kim, J. H. (2004). Intensive or extensive listening for L2 beginners? English Teaching, 59(3), 93-114.
Renandya, W. A. & Farrell, T. S. C. (2011). 'Teacher, the tape is too fast!' Extensive listening in ELT. ELT Journal, 65(1), 52-59.