What this shows, and what it doesn't
This is your public IP address - the one websites see when your device connects to them, assigned by your internet provider or shown if you're behind a VPN or proxy. It's not your device's private/local network address, and on its own it doesn't reveal your name or exact location, though it can be used to estimate a rough city or region.
Why this isn't your computer's actual local address
Every device on your home or office network also has a private/local IP address (often starting with 192.168 or 10.) used only for communication within that local network - that private address is never visible to the outside internet. The public address shown here is what your entire network presents to the outside world, which is a completely different number from your device's private one.
Why every device on the same network shares this number
A home or office router typically shares one public IP address across every device connected to it (phones, laptops, smart TVs, and so on), using a technique called NAT (network address translation) to route traffic between the shared public address and each device's own private address internally - which is why checking this tool from two different devices on the same WiFi shows the identical result.
Why a VPN changes what shows here
Connecting through a VPN routes your traffic through the VPN provider's own server first, so this tool (and every other website) sees the VPN server's public IP address instead of your actual internet connection's address - which is one of the main reasons people use a VPN, to mask their real public IP from the sites they visit.