The trouble with a "stranger's network" is you don’t know who is listening to the traffic passing by. A hacker might be present and capture your username and password to your email, Facebook account, or worse. Even on a “trusted” network like at work, you might want to 'cloak' your web activity.
A VPN (Virtual Private Network) is an encrypted tunnel going trough the internet. It is virtually transporting your online presence back home or to another trusted server. Using a VPN not only protects your internet traffic, but can also give you access to the internet in another country so you can see content, which is otherwise unavailable or hard to find.
You can create your own VPN or subscribe to a service like "Cloak". Unlike other services, the Cloak app will activate itself as soon as you connect to a new network. So, there is no chance that you forget to turn on the service. If you want have more countries available to gain local access you might want to check out VyperVPN.
If you don't want to rely on a 3rd party VPN and or need to safely connect to your own office network, I can install can configure a suitable Peplink router for you.