please i want to know ingeneral the difference between Client and Server Side and specially Difference between "SFTP Client Side" and "SFTP Server Side" and where i should be install SFTP client and SFTP server i i want to copy file by sftp command from server X to Server Y ?????
SFTP is FTP over SSH so if both servers are servers then both most likely already have SSH (if they are unix servers)
You then need an SFTP compatible client.
Since they are both servers It does not really matter which one has the client and which one has the server.
Typically one would use a client on a client machine, be it windows, Mac or linux to connect to the SFTP server on the server but in your case both are servers? then it really does not matter. one does the connecting while the other does the listening.
Perhaps you can provide a bit more info?