Do not trust the WiFi at that coffee shop or airport you frequent, as you never know if an evil hacker is parading around as a WiFi access point, hoping you connect and try to log into your bank, for example. They could also be sniffing all the traffic on the otherwise normal WiFi access point, scanning your PC for vulnerabilities, and more. Always use a VPN if you need to use free WiFi, use a firewall on your system, and keep everything up to date.