Each entree on Le Cellier comes with a side dish (e.g., wilted kale with the NY strip, mushroom risotto with the filet, etc.). Those are included in the price of the entree. You can usually substitute one listed side with an entree for another one listed with a different entree (e.g., if you wanted the mushroom risotto with the NY strip, you can usually do that because both a sides listed with an entree).
There are also seperately priced side dishes that you can order a la carte. Those are different from the sides that come with the entree and cannot be substituted.