Difference between CopyTo() and Clone() in C#

with Clone() the destination array need not exist yet since a new one is created from scratch.
with CopyTo() not only does the destination array need to already exist, it needs to be large enough to hold all the elements in the source array from the index you specify as the destination.

check here for example

http://geekswithblogs.net/dforhan/archive/2005/12/01/61852.aspx

you can also refer to msdn 

http://msdn.microsoft.com/en-us/library/system.array.clone.aspx

http://msdn.microsoft.com/en-us/library/system.array.copyto.aspx