It means Wireless networks.
There is nothing for them to share when it comes to cabled networks.
How the "Sharing" is done would be nice to know!
They have this on Windowsphone 8.1. I am not sure if it is the same or not, https://www.windowsphone.com/en-in/how-to/wp8/connectivity/wi-fi-sense-faq
They describe it:
Your contacts don't see your WiFi network password. For networks you choose to share access to, the password is sent over an encrypted connection and stored in an encrypted file on a Microsoft server, then sent over a secure connection to your contacts' phone if they use WiFi Sense and they're in range of the WiFi network you've shared. Your contacts can't see your password, and you can't see theirs.
If it bothers you turn it off.
