CALCULATE first expression: must be a measure?

Why does this measure works:

Medida = CALCULATE('Factos'[Faturação *];FILTER('Factos';'Factos'[PreçoUnitário]>=50))

Whereas this one doesn't:

Medida = CALCULATE('Factos'[Faturação];FILTER('Factos';'Factos'[PreçoUnitário]>=50))

The difference is that "Faturação *" is a measure while "Faturação" is a column.

By reading the DAX reference here, I can see the following remark:

The expression used as the first parameter is essentially the same as a measure.

So, what's the conclusion? That I must use a calculation as the 1st argument of the function?