A whois checker tool is important because it allows individuals or businesses to gather information about the ownership and registration of a specific domain name. This information includes contact details such as the name, address, and phone number of the registrant, as well as the date of registration and expiration, and the nameservers associated with the domain. This information can be useful for a variety of reasons, including verifying the authenticity of a website, tracking down the owner of a domain that may be infringing on your trademark, or identifying potential competitors in your industry. Additionally, the information provided by a whois checker tool can be used to ensure that the contact information associated with a domain is accurate and up-to-date, which is important for maintaining domain ownership and preventing unauthorized changes to the domain.