ICANN cannot administer every single domain in existence, so they delegate that to other entities. That delegation is segmented by TLD. Thus, TLDs indicate on

ICANN cannot administer every single domain in existence, so they delegate that to other entities. That delegation is segmented by TLD. Thus, TLDs indicate on who is responsible for administering the domain, and thus who to contact if something has gone wrong (e.g., if law enforcement wants to commandeer a domain). (At least in theory, I'm sure there are ambiguities in practice).