Many times you’ll want to know who is running a server that you find information on.
One solution is WHOIS. This used to be a broadly useful solution, but has gotten less useful in a world of masked registrations.
Another solution is to look and see what other sites are run from the same IP. This has some stumbling blocks as well.
WHOIS and IP sharing checks “jackpot” tools — when they work, they get you to high quality information fast. So they are often a good first stop. But expect failure.