You don't know who is monitoring network traffic when you browse the internet on public WLAN, for example in a café, at the airport, or in a hotel. With a VPN, you protect all important data such as passwords, banking details, credit card numbers, personal photos, confidential documents, simply all personal information. All your activity is encrypted through a VPN server, making it impossible to collect your internet metadata and no log of your browsing history can be created.