Everybody loves free stuff. We just can’t get enough of it. Free Wi-Fi is no different. All kinds of businesses in the hospitality industry use free Wi-Fi as an enticement to get you to come in and drink their coffee, eat their food, use their buses and so on.
Public Wi-Fi, even the not-free variety, is not secure. Others can see all kinds of information about your device and by extension you yourself as soon as you connect to a public Wi-Fi network.
If you absolutely must use a public Wi-Fi network, 1) also use a VPN to protect you from snooping and 2) please don’t do anything involving your financial information, medical information or, if possible, accessing your primary email account.