I would describe %LET as being the most simple way to creating a Macro Variable in SAS.
%LET variableName = variableValue;
Now, anywhere you use
&variableName, it will resolve to
NOTE:you may want to consider that
variableValueall on its own might bring you syntax errors, depening on what the value is and how it's used. For example, if it is a date and you're using it in the WHERE of a PROC SQL statement, it will need to be written as
"&variableName"dto work properly.