For situations where home runs from each camera back to the poe ports on the the nvr isn’t ideal, you can use a POE switch to reduce your cabling. Using a POE switch you can connect multiple cameras to one switch and then only have to run one ethernet cable back to the network that the NVR is connected to.
You cannot plug a POE switch into an NVR directly - it must be plugged into your network.
POE extenders can plug into the NVR ports, but you can only connect one camera into each POE extender. See our Using POE extenders to run long cable runs Guide for details on using POE extenders.