The Identity is a spatial operation and it needs two layers. This operation creates a new layer composed of the difference and the intersection between geometries of the two layers (A and B)

The resulting layer will contain all geometries generated by the DIFFERENCE (A - B) and the geometries generated by the INTERSECTION (A Intersection B).

The attributes of the resulting layer will have at least an ID, and a GEOMETRY. Besides that, other attributes from A and B can be chosen to compose the new layer. In this case, the geometries generated by the DIFFERENCE will have values only for the attributes from A, and the geometries generated by the INTERSECTION will have values for all attributes (A and B). 

It is accessed through:

Processing > Vector Processing > Identity...

1. Input Layer (A) : select one layer to use as reference.
• : Optionally, check this option if you wish to process only the previously selected objects in the map display.
• : Optionally, choose which attributes from layer (A) will be part of the output layer
  
2. Overlay Layer (B) : select other layer to compute the difference and the intersection and generate new geometries.
• : Optionally, check this option if you wish to process only the previously selected objects in the map display.
• : Optionally, choose which attributes from layer (B) will be part of the output layer.
3. Output Layer:  inform the repository by clicking on:
• to select the output directory and also inform the new layer name to store the result, 
•  to select the Data Source (giving its connection parameters).
• Layer Name: inform the new layer name to store the result at the data source.
4. Click OK to perform the operation or Cancel to close the interface.