So far, you've seen references to registries and registrars. It's important to understand the difference between them, and how you interact with these entities that exercise direct control over your domain names.
Your domain names are subject to, and impacted by, external and internal factors. Internal factors are the operation of the DNS and the management principles you apply to your portfolio. External factors come from registries under which your domains are registered and the oversight bodies that administer them. Those factors manifest on your portfolio via the conduit of the registrars for each given domain.
To effectively manage your portfolio, you must both be cognizant of, and understand, the influence of these external entities.
A domain registry operates a Top-Level Domain (TLD) for a given namespace .COM is a TLD. Your country has...