The TLS counterpart to 8080, and a very common choice for the management interface of a firewall, load balancer, appliance or application server — anything that needs an HTTPS admin panel without taking port 443 from the main site.
Often protected only by a default password, and often running an out-of-date TLS stack because the appliance is rarely updated.
Usually a management interface on an appliance. Check whether it still uses default credentials and whether the device has firmware updates pending.
The port scanner will tell you whether 8443 is reachable on a host you control. Checking from outside your own network matters: a port can be open on the machine and still be blocked at the firewall, and it is the view from the internet that decides whether anyone else can reach it.
Only scan hosts you own or have permission to test.