Hello Samah,
QUERY_DOCU.GUIDES is a variable VARA.SQLI object and the "select query" to the database is written there.
This variable "QUERY_DOCU.GUIDES" is being used in the Data Reference of the promptset for the Guide Drop-Down line item and that field has also been marked dynamic.
So whenever the promptset is activated, it calls the QUERY_DOCU.GUIDES for fetching the query result each time dynamically.
Thanks,
Arun