This is a data source for the DNN FormAndList (FnL) module - formerly known as User Defined Table (UDT).
This is an installable DNN module which adds a DataSource to the VisualQuery providing FnL data.
To read more about it, read the release blog post https://2sxc.org/en/blog/post/formandlist-datasource-as-standalone-dnn-extension