A domain is a name on the internet (for example edis.at) and can be used for a website address (www.edis.at) and for email addresses (e-mail@edis.at).
From the technical point of view, a domain name is the translation of a technical IP address (for example 213.229.30.35). This is a numerical code that computers need for communication on the internet. Each domain is a unique element all over the world, otherwise no content could be clearly identified. A derivation would be to use names (vanity telephone numbers) instead of telephone numbers which has already partially been realised by taking the 0800 numbers PROVIDER.