VPN ( Virtual Private Network ), just as the name says it's a virtual network like your default  physical network. Let's focus on the word virtual, here it means it's not an alternative to your physical network, so it needs the physical network to work. It acts as a physical network over your actual physical network and gets you running on the internet. It has its own advantages and disadvantages, like no one can track you while you use VPN but it's a  little bit slower than default connection as it encrypts your data for which it can't be traced easily.