These include leaf vegetables (e.g. Lettuce), stem vegetables (Asparagus), root vegetables (Carrot) and flower vegetables (Broccoli), and botanical fruits such as green beans, cucumbers, squashes, pumpkins, tomatoes, avocados, capsicums, et cetera, as well as fleshy, immature seeds such as those of peas or beans.
Vegetable is not a botanical term and so there is no contradiction in a plant part being a fruit botanically while still being considered a vegetable.
In general, vegetables are thought of as being eaten in the main course, not as Dessert or Breakfast (with some exceptions, such as Rhubarb).
Commercial production of vegetables is a branch of Horticulture called olericulture.
Vegetable is also used as a literary term for any plant: vegetable matter, vegetable kingdom.