If you are the type of person who would think about going to an underground restaurant then you will like Dining Under the Table.
-From a review of an underground restaurant in Silver Spring
In economics we often make an assumption that everyone has the same preferences, let's just say we can assume the reviewer and me along with my wife and the reviewer's wife have similar preferences.
Underground restaurants avoid some of the fixed costs of being a restaurant. The benefit is that they can have smaller number of diners (for example under the Table has 6). It can also allow people to cook and experience the pleasure of serving good food to people, without fully investing in a restaurant.
There are draw backs of underground restaurants too, but the reviewer's description of the meal sounds too good to worry about that for the moment.