C/O in a letter address ?

Hi I am just curious what does a C/O in a letter address? Example:





Mr. John Doe


C/O Mr. John Smith


1458 Made Upaddress Lane


Nowhere, NY 95475





Any help is appricated. Thanks

C/O in a letter address ?
C/O stands for Care Of.
Reply:lets say you were staying at you uncles' or a friends' for summer vacation and I wanted to send you a letter or birthday card. I would send it to you, (Mr. John Doe) "in care of" or [C/O] for short, to your uncle, (Mr. John Smith). This allows the postal carrier to deliver your mail to someone other than yourself.
Reply:C/O = care of


Mean the letter will or should be given directly to the C/O.