What is 'currentHost' for, in defaults?

There are many webpages given over to listing defaults commands in order to configure various parts of the OS. Some of them include the flag -currentHost. The man page for the defaults command documents the option -currentHost, as *"restricting preferences operations to the host that the user is currently logged in on."* Similarly, the -host flag allows a hostname to be specified for the preference. What is the purpose of explicitly setting these flags? Under what circumstances would a preference affect some other host? (Or indeed, when would a user be logged in on a different host?)