DAX CODE Understanding

All respondents no brand (brand info) =
CALCULATE (
    SUMX (
        DISTINCT ( 'factBrandAwareness'[ObservationGUID] ),
        FIRSTNONBLANK ( 'factBrandAwareness'[Weighted], 0 )
    ),
    ALL ( 'dimBrandsByCountry'[Brand] )
)

Hi All

I am new to Power BI and DAX, I have the above code in an existing report I have picked up, would someone be able to break down what this doing on a generic level?

Thx!