Inherit Source
When a source is set at the element level, the options Inherit Current Node and/or Inherit Parent Node will appear based on the source relationship.
Inherit Current Node
This option is available when the source is set in the same node where the field is being mapped. If the source is multi-item the node will be multiplied and the fields will inherit the data from the current iteration.
Inherit Parent Node
This option is available when there is a source set in a higher-level node from where the field is being mapped. It is possible to inherit from a parent node while there is a source set in the current node, and even mix both using composed sources.