Mac Norton Message - The service "applications" is starting on your Mac. If you don't change firewall settings, the firewall will block connections from other computers to this service on your Mac

All of a sudden we are getting this warning on our Macintosh and a similar one on my Windows 10 machines.  Why would I want to allow other computers to use anything on my machine?

What are the implications for this setting?

Thank you for your response.

Becky