The $args variable is an Array and it contains each of the arguments that you passed to your widget when you called it.
How you use the $args Array within a widget greatly depends on what exactly that widget's purpose is, but here are two (untested) examples.
eg. If you have a widget named doit and you call it in your passage like so.
<<doit "one" "two" "three">>
... then the $args Array avaiable to the doit widget will contain the three arguments ("one", "two", "three") you passed to it.
eg. You can used it's length property to check how many arguments were passed to the widget.
/* Check if enough arguments were passed to the widget. */
<<if $args.length < 3>>
You need to passage 3 arguements to the ''doit'' widget.
eg. you can use integer indexes to access each argument. (Array's are zero based, 1st index is 0, next is 1, etc)
<<set _first to $args>>
<<set _second to $args>>
<<set _third to $args>>