What a domain-to-IP lookup shows
Every domain name is really just a human-friendly alias for one or more numeric IP addresses - this looks up exactly which addresses a domain currently points to, the same lookup your browser silently performs every single time you visit a site, just made visible and explicit. A domain can resolve to multiple IPs at once (common for sites behind a CDN or load balancer), and both an IPv4 and a newer IPv6 address can exist side by side for the same domain.
Why a domain can resolve to several different IPs
Larger, high-traffic sites typically spread their traffic across multiple servers or route through a content delivery network, so the same domain can legitimately return different IP addresses depending on server load, your geographic location, or ongoing load-balancing decisions on the provider's end - none of these multiple results indicate a problem.
IPv4 vs. IPv6, side by side
These are two separate addressing systems running in parallel across today's internet. IPv4 is the older, much more widely deployed format, built on a fixed pool of addresses that has long since run low on unallocated space. IPv6 is the newer format designed specifically to provide a vastly larger pool of possible addresses. A domain may have records for one, both, or - in rare misconfigured cases - neither, which is why this tool checks and displays both separately.
Common reasons to look this up
Confirming DNS changes have actually propagated after updating a domain's records, diagnosing whether a site resolves to the server you expect it to, or simply satisfying curiosity about the real infrastructure behind a familiar domain name.