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Consumed is the amount of memory that has been allocated to the VM by the host. Active is the amount of memory currently being used.
With RedHat in particular (from my experience), the OS does not send the signal to the hypervisor telling it that it is done using a particular bit of ram - because of this, the hypervisor never deallocates the ram, and the host reports it as being consumed.
The simplest way to see what RedHat is really doing under the hood is to get on the machine and run something like top or htop to see what's taking up the memory (if anything at all).