Perhaps I'm missing something, but I've never understood what it means to be connecting to an "unsafe" wifi point. Isn't most of my data ultimately going over

Perhaps I'm missing something, but I've never understood what it means to be connecting to an "unsafe" wifi point. Isn't most of my data ultimately going over the Internet unencrypted anyway? Does this just mean there's no firewall blocking traffic on certain ports between me and bad guys?