The tool strips the hostname down to its registrable domain and queries the registry's RDAP service for it. From the response it reads the registration, expiration and last changed events, the registrar entity and its IANA ID, the domain's EPP status codes, the delegated name servers, and whether the zone is DNSSEC-signed. Age is calculated from the registration date to today in years and months, with the total in days shown alongside.
What to look for
For your own domains, the expiry card is the one that matters: it turns amber under 30 days and red once lapsed, and a lapsed domain moves through a grace period, a redemption period and then deletion, getting more expensive to recover at each step. For a domain you are evaluating, compare the registration date with how old the site claims to be, check the status list for holds or pending deletion, and note the name servers — they tell you where the site is hosted and whether that has changed hands. The registrar and name servers are also the starting point when you need to contact whoever runs a domain, since registrant details are redacted.