This stands for the holder of a Second Level Domain. SLD is the technical term for domain name. A Registrar is an organization that registers domain names on behalf of a Registrant. Signature Domains is a Registrar. Each entry in the Registry contains a domain name, showing its TLD, the date it was registered and the date the registration expires, as well as the name of the registrar who sponsored that domain name and placed it in the Registry.
Whois service provides information about the registrant of a particular domain name.
Your information will show up after the central registry whois performs its update. The whois is updated by the central registry once a day. Other servers may not show your updated information for a period of 24 to 48 hours. The response from the Registry will be displayed right away. I still have more questions.