Re: General
Cloning is where a clock-gate (a special gate in the clock tree that switches of the clock signal to a number of flip-flops to save power when they are not needed) is duplicated so that one clock-gate driving, for example, 40 flip-flops can be "cloned" to become 2 clock-gates driving 20 flip-flops each.
A buffer is a basic electronic gate that serves to strengthen a signal. It is needed when you wish to drive a signal along a long wire, or when you want to drive a signal to very many receiving pins. A single driving gate can only drive a short length of wire and only a small fanout. Buffering is the insertion of buffers to help drive the signal to bigger loads.