.example

The name example is reserved by the Internet Engineering Task Force (IETF) as a domain name that may not be installed as a top-level domain in the Domain Name System (DNS) of the Internet.
Reserved DNS names.
By publication of RFC 2606 in 1999, the Internet Engineering Task Force reserved the DNS labels "example", "invalid", "localhost", and "test" so that they may not be installed into the root zone of the Domain Name System.
The reason for reservation of these top-level domain names is to reduce the likelihood of conflict and confusion. This allows the use of these names for either documentation purposes or in local testing scenarios.
Purpose.
The top-level domain is explicitly intended to be used in documentation or other technical writing, when domain names are presented as examples in usage or presentation of concepts of the Domain Name System or the Internet.