What is options parameter in Folder.Files(path as text, optional options as nullable record)

In Power Query documentation we find description: 

Folder.Files(path as text, optional options as nullable record) as table

Returns a table containing a row for each file found at the folder path, path, and subfolders. Each row contains properties of the file and a link to its content.

Wonder where I can learn what the second parameter "optional options as nullable record"  is, what it does and how to use it? After lot of googling I can not find any place where this information is provided.

Is the maybe a possibility to use this parameter to instruct Folder.Files() function to get fonly files of a certain type?

Anyone knows what second parameter options  for Folder.Files() function is and there is this documented?

Example:

let
    // Definition at: https://docs.microsoft.com/en-us/powerquery-m/folder-files
    //
    // Folder.Files(path as text, optional options as nullable record) as table
    //
    // What is options? Where to find description? What do it do?
    //

    Options = null,
    Source = Folder.Files("C:\Users\Dan\Favorites", Options)
in
    Source