WHOIS is a query and response protocol used to look up information about registered domain names and IP addresses. WHOIS records contain details about who owns a domain, when it was registered, when it expires, and the name servers it uses.
A domain WHOIS lookup returns registration details including the registrar, creation and expiry dates, name servers, and domain status codes. This information is maintained by domain registrars and is publicly available through WHOIS servers.
An IP WHOIS lookup returns network allocation details - which organization owns the IP block, the network range, the Regional Internet Registry (RIR) that allocated it, and contact information. IP allocations are managed by the five RIRs: ARIN, RIPE NCC, APNIC, LACNIC, and AFRINIC.