Q:

Why couldn't I get onto the client's server through FTP?

I had a client that ultimately had to give up on because I couldn't for the life of me access his server. I tried through FileZilla and FireFTP.
He then told me that it's a Linux server and I need to access it through the SSH. 
I was completely confused and I told him that maybe his password or hostname was not working. He said I needed something called "PuTTY" I checked it out but it was for windows and I am on a mac.
Can someone explain to me what this is all about or point me into the right direction where I can get a better understanding. I tried to research but I am not sure exactly what I am looking for.

A:

SSH is a secure methode of accessing a server. Files can be uploaded using sftp (not to be confused with FTPS). When connecting to a SSH server using ssh user@host, you'll be presented with a command line. If you do not know how to upload a file in this way, use a graphical SFTP client.
Filezilla is capable of SFTP. Depending on the security-awareness of your client, you need to add a private key, given by your client. Select SFTP as method (not FTP), enter the username and host provided by your client. If necessary, change the default port of 22.
For a software recommendation, try https://apple.stackexchange.com/ or https://superuser.com/

