請問C/O 同O/B 是什麼意思

Are you talking about “care of” and “on behalf” ?
They both have the meaning that someone was doing a job for another person. There is virtually no difference in term of usage. There is another one also have the same meaning : p.p
Example :
Best Regards
___________
Cindy Leung – the person who sign the document
c/o Tong Wong – the person who is supposed to sign the document, normally he is the boss of Cindy
o/b and p.p have the same usage.

Hi, they are not the same.

[c/o] = care of; normally use in the address; e.g. u are living in Peter home, but the register address name is Peter, u do not want postman get something wrong, then u have to write as ....

your name
c/o Peter XXX
(peter address)

[o/b] = on behalf of; normally use in the letter; e.g. u write a letter for ur company; at the end of content, u should write as ....

Yours faithfuly
On behalf of (your company name)



(your name)