VPNs and public WiFi
A VPN is often sold as a cure for everything. It is useful for one job, and knowing which one stops you relying on it for the wrong things.
What a VPN does
A VPN encrypts the connection between your device and the VPN company's server, and your traffic reaches the internet from there. People on the same network cannot read it, and the sites you visit see the VPN's address instead of yours.
What it does not do
A VPN does not make you anonymous: the VPN company can see your traffic, and any site you sign in to still knows who you are. It does not stop phishing, fake websites or malware either.
Public WiFi
Most sites already encrypt your connection, which is what the padlock and https in the address bar show. The bigger risk on public WiFi is a fake network with a convincing name. Ask staff for the exact network name, and use your phone's mobile data or hotspot for banking and anything sensitive.
Choosing a provider
A VPN moves your trust from the owner of the WiFi to the VPN company, so choose one you can look into. Look for a paid service with a published independent audit, a clear no-logs policy and a real company behind it. Be wary of free VPNs, which have to make money somehow.