XCOPY is a vmware primitive part of the VAAI commandset, it is an offload command for copy where the copy is sent to the storage array rather than relying on the host resources to do it.  It's typically involved in storage vMotion or in Clone of VM operations,  Linux and Microsoft also take advantage of this.  Google VAAI and you will learn more
can anyone help me with what is xcopy session, why these sessions are created.
XCOPY SESSION