WHOIS (pronounced as the phrase “who is”) is a query and response protocol that is used for querying databases that store an Internet resource’s registered users or assignees. These resources include domain namesIP address blocks and autonomous systems, but it is also used for a wider range of other information.

What does this mean in practicality? You put in the domain name, and it tells you information about who owns and administers it.

Perform a whois query: