A WiFi network administrator or owner can see the domains (websites) you visit and the amount of data used, but they generally cannot see your specific "app history" or the exact content within those apps. Because of modern encryption (HTTPS/TLS), the details of what you are doing inside an app—like specific messages, passwords, or photos—are hidden from the router. However, they can see that your device connected to "https://www.google.com/search?q=api.instagram.com" or "netflix.com" and at what time. To prevent this "metadata" from being visible, you should use a Virtual Private Network (VPN), which encrypts your traffic before it even reaches the WiFi router, making your activity appear as a single, unreadable stream of data to the network owner.