What is the LinkedIn Audience Network?
The LinkedIn Audience Network is a list of 3rd party websites and mobile apps your ads are eligible to show on if you have it enabled. That means instead of your ads showing on LinkedIn, they will show on other publisher sites and apps.
This is similar to the Google Display Network.
I recommend turning off the Audience Network as the engagements are low quality.
If you are curious and want to see the full list of publishers on the Audience Network, you can download the publisher list by going into your campaign manager account, plan section, selecting brand safety, and downloading the publisher list for web and mobile apps.