COUNT, COUNTA, COUNTAX, COUNTX – DAX Guide

COUNT: Counts the number of rows in the table where the specified column has a non-blank value.
https://dax.guide/count/

COUNTA: Counts the number of values in a column.
https://dax.guide/counta/

COUNTAX: Counts the number of values which result from evaluating an expression for each row of a table.
https://dax.guide/countax/

COUNTX: Counts the number of values which result from evaluating an expression for each row of a table.
https://dax.guide/countx/

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