A domain path is a series of three-character codes separated by a slash delimiter that uniquely identifies a domain. Each digit in the three-character code consists of one of the following 60 possible characters:
#$&()*+,-.0123456789:;<?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[]^`}|{~
Its more detailed in wiki:
Domain Separation - ServiceNow Wiki
