ICANN is the Internet Corporation for Assigned Names and Numbers, a nonprofit multistakeholder organization established in 1998 that coordinates the management of the internet's core identifier systems: domain names, IP address allocation, and protocol parameters.
ICAANN operates through IANA (Internet Assigned Numbers Authority), which performs the technical administration of these systems. At the domain level, ICANN accredits domain registrars who sell domain registrations to the public, and contracts with registry operators who run the authoritative servers for each top-level domain (both generic TLDs like .com and .org, and country-code TLDs like .uk and .de).
When you register a domain, your registrar enters it into the registry's database and publishes nameserver information via NS records. ICANN does not issue or validate SSL/TLS certificates—that is the role of certificate authorities. It also does not directly resolve trademark disputes; those are handled by dispute resolution providers under ICANN's Uniform Domain-Name Dispute-Resolution Policy (UDRP).
ICAANN's role is to ensure the DNS root zone and delegations function reliably, maintain the EPP code standard that allows domains to transfer between registrars, and set minimum standards for registrar conduct (such as requiring registrar locks and managing redemption grace periods for expired domains).
TipICANN doesn't control website content or take down domains. If a domain violates laws, law enforcement and hosting providers act—not ICANN.