DNS (domain name system) is a service that translates IP addresses into more easily readable formats for humans. A website like thedonald.win could have a public IP address of 178.56.223.45, but that's really hard to remember, so DNS just turns it into thedonald.win. The IP number you see is the public IP address of the service's DNS server. There are different public DNS services with google's (8.8.8.8) being the biggest.
You can see what your DNS server is by looking at the settings of your home router.
The supreme court defers to the legislative/executive branches of government to enforce decisions.
Trump would likely have to send US Marshals if they don't comply.