I would like to add that it's important to be clear what is meant by "vegetables". The word can mean very different things in different contexts.
Scientifically (in botany, biology or nutrition), "vegetable" means "plant" - all food not derived from an animal. But in colloquial usage, "vegetable" means a small and badly defined subset of that. Wikipedia describes this kind of vegetables as plant food that is not "fruits, grains, or nuts". (Wikipedia also notes a third "culinary" usage, where "vegetable" means "any edible part of a plant with a savory flavor"; I'm not sure what that even means - presumably the usage of "savory" is not the colloquial one!)
In colloquial use, "vegetables" are opposed to "fruits" and distinct from "nuts", "berries" and "grains". Of course, many such "vegetables" are also botanical fruits (like tomatoes), and so are all berries and nuts; grains are the seeds of fruits.
Many (most? nearly all?) of the benefits that can be obtained from eating colloquial!vegetables can also be obtained from at least some other plant food. There's a huge difference between a diet of only animal food, and a diet that contains everything except colloquial!Vegetables which are "not fruit".
Wikipedia also notes a third "culinary" usage, where "vegetable" means "any edible part of a plant with a savory flavor"; I'm not sure what that even means - presumably the usage of "savory" is not the colloquial one!
It basically means the kind of plants that you use in a main dish in traditional cooking.
You can use apples in a salad but you don't serve spaghetti with apple soup.
This is a thread where people can ask questions that they would ordinarily feel embarrassed for not knowing the answer to. The previous "stupid" questions thread is at almost 500 questions in about a month, so I think it's time for a new one.
Also, I have a new "stupid" question.