ICANN is the technical and policy body that runs the root level of the internet's namespace. They:
- Accredit registrars (companies allowed to sell domain registrations) like Tucows/OpenSRS, GoDaddy, Namecheap.
- Run the IANA functions (assignment of top-level domains, IP address blocks, protocol parameters).
- Set consensus policies all registrars must follow: UDRP, Transfer Policy, ERRP, WHOIS Accuracy Program, etc.
- Maintain the root zone file (the list of every TLD and who runs its registry).
ICANN is California-based, non-profit, and runs on a multi-stakeholder governance model: registrars, registries, civil society, governments, and end-user advisory committees all have input.
The fees you pay for a domain include an ICANN fee (currently $0.18/year for most gTLDs) collected by your registrar and remitted upward. It's small but it's why ICANN exists.
