What the Media Library Is and How To Use It
When you start to add media to your Posts and Pages, you may find that trying to keep track of uploaded media can prove cumbersome. That is why WordPress has supplied us with the Media Library.
When you add files to your Posts and Pages, they are automatically stored in the Media Library. Most of the time, this will not affect your workflow and you can continue adding your content as you normally would. Sometimes, you may want to use those same files in another Post or Page on your site. Rather than re-uploading the same files and taking up more space, they can be found in your Media Library.
To see the aforementioned files and Library, navigate to Media -> Library from your Dashboard. In this new page, you will see every file you or your users has ever uploaded on your site. (Note: As a contributor you have no access to the Media Library nor can you upload media.) From here, you can delete, upload, or edit all files all in one place.
To add files from your Media Library to your Posts and Pages, you can also add on an individual basis.