LM5069EVM-627: GND and SGND

Hello team,

I have a question about LM5069EVM-627 schematic. (Figure-18 on the user's guide)
What is the main difference between GND and SGND?
They are not distinguished on the datasheet typical application schematic.
I'd like to understand which we should refer to with the technical background.

Thanks in advance.
S.Sawamoto