Legacy Windows name resolution on a local network, from the era before Windows relied on DNS. It answers questions like 'which machine is called ACCOUNTS-PC' by broadcasting to the local segment, which is why it never worked across the internet and was never meant to.
Leaks machine names, workgroup and sometimes user names to anyone who asks. Block at the network edge without exception.
Exposed NetBIOS is a straightforward information leak. Block it at the perimeter and assume your machine names and shares have already been catalogued.
The port scanner will tell you whether 137 is reachable on a host you control. Checking from outside your own network matters: a port can be open on the machine and still be blocked at the firewall, and it is the view from the internet that decides whether anyone else can reach it.
Only scan hosts you own or have permission to test.