Hibernate-Snapshot device

I would like to know how the snapshot of the system is taken during
hibernation(S2disk) which is then stored in the swap partition.
A typical /etc/suspend.conf shows that the snapshot device to be used is
set to /dev/snapshot. Please suggest something to make my understanding
better as to  how the snaphot image is created and exactly how it is stored
at its position which is then loaded into memory on resume(resume device
parameter embedded into initramfs).