ICANN – manages domain system
Registry – the wholesalers of domains; NOT supposed to sell to the public. Verisign famous as the registry for dot com, dot net, and dot tv, among others. Operates two of the internet’s 13 root nameservers. Accordingn to Wikipedia, “The root servers form the top of the hierarchical Domain Name System that supports all Internet communication.” Neustar is the Registry which manages dot us and dot biz. Public Interest Registry, PIR.org, is the registry for dot org.
Registrar – entity that manages the reservation of domain names by the public. The go-between registries and the public, like the public can buy RETAIL, but not WHOLESALE. Godaddy, eNom, NameCheap, NetworkSolutions. You, the Registrant, buy from the Registrar.
Registrant – the public, us, me. We purchase through Godaddy, DomainIt, or NameCheap, same as we buy from retailers, instead of direct from Verigisn or Neustar.
The syndicate behind ICANN, Verisign, and the major Registrars exploits small US businesses who believe the identity of their online presence is government-ensured, while it plans takeovers and puts obstacles in the path of honest business people, to separate them from their valuable dot com domains.
It does this by targeting a domain name.
REf: Domain Name Registrar – Wikipedia entry