What is the difference in meaning when a comma is present before 'including,' or 'such as,' and when it is not?

With the comma, the following phrase becomes parenthetical, that is it is unrestrictive, added information.
It depends on whether or not the added material is essential or nonessential. Is it necessary to the meaning of the sentence...or just thrown in as additional information? If it's essential, no comma. If it's nonessential, comma.