If you know someone rather well, you say

"Wie geht es dir" - "How are you?"

but if you don't know him, you say

"Wie geht es ihnen?", which literally means "How are they?"

Also, back in the old days, you would talk to the nobility in plural.

"Wie geht es euch?", there is no equivalent in English I guess, since you is plural and singular, "How are you?"