i want to learn something about ssh, especially the command, can anyone of you tell or provide me documentation, web site that teach us all those ssh commands:( ?

SSH is a piece of software that connects you to a Linux console. For an introduction to Linux commands, take a look at this link (http://www.google.co.uk/search?hl=en&q=Basic+linux+commands)

Thanks,
Alan.

so if i need to run dedicated server for my hosting business, i need to know these command very well, right?:(

You may want to look into a Reseller Account first.