Confusing them is the single most common source of trouble when something breaks.
It is what somebody types. You rent it yearly from a registrar, and it points wherever you tell it to point.
A server where the files live. Without hosting the address leads nowhere; without the address people have to know the server's IP.
The pages, images and code that sit on the hosting. You can rebuild it entirely and keep the same address.
Your domain can be registered with one company and your hosting bought from another. Keeping them together is simpler, but nothing requires it.
Reading elyspace.com from right to left.
Also called the TLD. Some are open to anybody, some are tied to a country like .in or .uk, and some have eligibility rules. It affects trust more than it affects ranking.
The part you choose. It has to be unique within that extension, which is why the same name can exist on .com and .in as different owners.
A division of a domain you already own. You create them yourself at no extra cost - blog.yoursite.com needs no second registration.
The setting that says which hosting the domain points at. Changing host means changing this, and it is why a move takes a few hours to propagate.
Registering one, and what goes with it.