Per https://docs.netapp.com/us-en/trident-2110/trident-use/ontap-nas-examples.html, the management LIF in question is the "IP address of a cluster or SVM management LIF". Cluster management is a separate IP space and has a separate volume (root volume) for it's purpose. It is kept separate from the data SVMs to keep ONTAP config and logs as well as ensure cluster stability. SVM management is less frequently used but can be used for things like VScan, FPolicy, etc.
Thank you for the reply but why do I need to specify a managementLIF in my backend definition? I have a dataLIF, user and password specified. I have not found anywhere in the docs that says why I need to specify the managementLIF. My guess is that when I create the backend that maybe the managementLIF and root volume are accessed to get some metadata but this is just a guess.