Agentless Snapshot Question

Rapid Recovery 6.2.1...esxi 5.5...if i decide to do agentless on some of my servers, what is the method of the snapshot being created? I know the agent uses VSS and the local RR logs to know what to backup in each snapshot in windows but wasnt sure how Rapid Recovery knwos what has changed when backing up via VMWare agentless. I did notice in the setup of the core a mention about merging vmware i wasnt sure if using snapshots was how the agentless backup worked with VMWare