I have VMware vSphere 6 Enterprise Plus several licenses for multiple hosts and n.1 vCenter Server; now I bought n.2 new licenses but I found out to be "vSphere with Operation Management 6 Enterprise Plus".
It's vRealize Operation management or this one is another product?
About license I can install Operation Management even if there are more 2 hosts ?
You can deploy and licence vrops standard edition but only monitor the VMs and hosts that have the vSphere with Operation Management 6 Enterprise Plus licence key.
take a look at https://www.vmware.com/content/dam/digitalmarketing/vmware/en/pdf/products/vsphere/vmware-vsphere-wi... to see what you get with that key
vSphere with Operation Management 6 Enterprise Plus (vSOM) is a vSphere Enterprise Plus license that also licenses you for vRealize Operations Manager (vROps).
You can install vRealize Operations Manager and enter the vSphere with Operation Management 6 Enterprise Plus. The hosts monitored by vRealize Operations Manager would be limited to the number of sockets of vSOM currently owned.
You can always upgrade you other keys to vSOM to get full use of vROps.