Purposes of gardens....

Food gardens would, of course, contain plants that can be used to feed us, and perhaps our pets (I need to grow different types of plants and grasses in order to give my Tortois, Hazel, a healthy diet).  I believe in organic gardening and permaculture, so I wouldn't like to see a food garden planted in rows, fed with harmful fertilizers, and protected with pesticides.  I would like a more natural garden, perhaps with more native food plants.

Ornamental gardens just have plants that look nice, but don't really serve any other purpose.  This would be like my manager's garden.  Even though she might have some useful plants in there, she doesn't know about them and her garden is just to look at, according to her.  Rock gardens are probably more ornamental, and contain rockery of choice and, to me, should have grasses and succulents growing in them.

Medicinal gardens would contain plants that have significant medicinal values.  I would think this would be more of a permaculture layout, also.  I don't personally know of any medicinal plant gardens, but I am planning on starting one in my dog yard.  They crawl under the fence and get out, so I thought that I could plant and herb and medicine garen around the inside perimeter to stop this.  It would be useful and effective, and benefit all of us here.

Hence, herb gardens.  Same story as above. 

I really don't think you should just have one kind of garden.  I believe it would be more worthwhile to have food, medicine, and beauty growing all together in harmony.  Doesn't that make more sense?  I also believe that a forest is a garden.  As in The Earth's Blanket, Native Peoples got everything they needed from the plants that grew naturally around them.  If they didn't have something, they could trade another tribe for them.