.internal

String Information
A-label ASCII form of the domain name, which is used internally in the DNS to represent this domain using the IDNA protocol
internal
Category Classification based on purpose and governing global allocation policy
Special-use top-level domain
Script The writing system (script) used for this domain label
Latin Latn
Status The current delegation status of the string
Reserved
Technical Status
Not delegated
Remarks
Reserved for use in situations in which private network operators may wish to use their own domain naming scheme that is not intended to be used or accessible by the global domain name system (DNS), such as within corporate or home networks.

For further information, see A Top-level Domain for Private Use (draft-davies-internal-tld)