A public network hides your PC from other devices in the network, like a phone, etc. for enhanced security. A private network is discoverable by other devices in the same network. So, if you are sure of the devices connected to your network and use files/links back and forth between devices, you can choose Private. If you are not sure about other devices connected to your network or have unknown devices, better to keep it Public. Note that you wont be able to connect your PC to your phone in Public network. There are other ways to connect though.