The image shows a Description for Function dialog box, which has the following text:
Returns the value of inputString after translating every character to its lower-case correspondent. Usage: xp20:lower-case(inputString as string) Example: xp20:lower-case('ABcId') returns 'abc!d' For more information please refer to this page.
The word page is the link to function's description at the World Wide Web Consortium at www.w3.org.