What goes behind the scenes when a new client is created?

Hi Basis friends,

I am not a Basis person rather I am SAP HCM functional person. We have to load data in SAP and need a new client for DEV and Quality. I was wondering what goes on your side of the world while creating a new client. You can give me both the scenarios where you are copying data from one client and transferring to the new client. Please explain in the terminology so that I can understand.

Thanks a ton,

Pankaj