What is a domain exactly?

[Nomad]

A domain is the unique address that identifies a website on the Internet. It typically consists of a name (such as "example") and a domain extension (such as ".com" or ".org"). For example, the domain name for for discussiuon hub is discussionhub.net. A domain will become live (is publicly accessible) only when it is hosted. This brings us to another follow up question what exactly is hosting?