The LET function assigns names to calculation results. This allows storing intermediate calculations, values, or defining names inside a formula. These names only apply within the scope of the LET function. Similar to variables in programming, LET is accomplished through Excel’s native formula syntax.
https://support.microsoft.com/en-us/office/let-function-34842dd8-b92b-4d3f-b325-b8b8f9908999

