This is an inbuilt function function provided by PPWIZARD.
This function takes a single parameter and returns it in lower case. The translations are performed for english characters (a-z) by default but it is possible to configure PPWIZARD for other languages.
To convert to upper case you can use the ToUpperCase() function.
Note that for more complex character translations you should have a look at the standard rexx translate() function (which this what this function uses internally).
To configure the case conversion see the "Upper/Lower Case Configuration" section.