Resource Fencing is fencing at resource granularity. It ensures exclusive access to a given resource. Common techniques for this include changing the zoning of the node from a SAN fiber channel switch (locking the node out of access to its disks) and things like SCSI reserve. Resource fencing is implemented differently depending on the type of resource and how access to it is granted, and hence can be denied.
Compared to Node Fencing, where we prevent a failed node from accessing shared resources entirely, it has finer granularity, alas not all resources support this functionality, or it might have some limitations that keep it from being useful in a particular situation.