"Tell me about him."
अनुवाद:मुझे उसके बारे में बताओ।
उस is the oblique form of वह and refers to just one person, while उन is the oblique form of वे and refers to multiple people or is used to show respect when referring to a single person.
- उसका = his/her/its eg उसके कुत्ते - his dogs, उसकी किताब - his book.
- उनका = their eg उनके कुत्ते - their dogs, उऩकी किताब - their book.
But उन is also used for respect: वे मेरे पिता हैं, उनका नाम अजय है - that is my father, his name is Ajay. We are using उनका to show respect.
Both मुझे उसके बारे में बताओ and मुझे उनके बारे में बताओ are acceptable here as translations of "tell me about him" - the first one being casual and the second one being respectful.