They basically deliver food--not necessarily complete meals. But, yes, a lot of restaurants use them for food delivery. Probably not at the highest end but they can be pretty decent given good food prep.

I don't know where you want to draw the line but imo they get pretty close to complete meals (https://foodie.sysco.com/) especially when it comes to desserts and appetizers.

The desserts are where I can tell the most since one restaurants lava cake is often dangerously close to every other mid tier restaurant.