Hey @Th,
Thanks for reaching out. Those shortcode arguments work the same as any other, so in this sort of format:
before_widget=""
Now, what you put between the quotes there simply gets displayed in certain places depending on the argument.
So let’s say you have this shortcode:
[tribe_events_list before_widget="here are some events!"]
Well, then the text “here are some events!” will display before the widget:

A title argument adds a title; before_title and after_title add strings before and after the title; and so on.
If you’re curious how they all work, I recommend putting a widget shortcode in a sample page, and just tinkering around a bit, experimenting with the different attributes. It’s the best way to see what they do.
I hope this information helps,
George