Why does it say unsecured network (when at hotel for instance)and is that bad?

It says that because the security protocols used on that network, if any, are no longer considered secure.

This should not present a problem in most cases as most web sites and apps establish a secure connection between your device and the server, however, you should take caution and make sure that the web sites you access are secure when using that network. You should see a padlock icon in the address bar of the browser indicating that the connection is secure. If you do not, do not enter any personal information into forms on that site as it is sent in the clear and can be intercepted and read by anyone on the network with the proper tools.