show interface switchport command shows a specific row
Pruning VLANs Enabled. The field description is
Lists the VLANs that are pruning-eligible but I cannot understand what that row is meaning.
With VTP, you can mark VLANs as eligible to be pruned for a trunk link. When pruning is enabled in VTP, the eligible VLANs will be pruned if there is nothing downstream of the trunk link using those VLANs.
This Cisco document shows how to configure VTP pruning and how to add VLANs to the pruning eligible list.
switch(config-if)# switchport trunk pruning vlan [add | remove | except | none | all] VLAN-IDs
It is a good practice to prune VLANs from links where they are not needed. This will eliminate broadcast traffic for those VLANs being sent to switches which don't have those VLANs.