Is vpn like wifi?

Not really, no. A VPN (in the sense that I know it) is a virtual private network. What they're generally used for is to allow you access to services. For instance, say a certain service is only available if you have an IP address belonging to your company (a company intranet, for instance). The company may make certain IP addresses available for VPN and then, when you're at home and on your own ISP (or phone) you can use VPN software to temporarily get access to one of the VPN IPs and, with that, the intranet. It's not an internet connection as such, it's a disguise to pretend you are part of a network that you aren't.