Nightshade refers to a family of plants known as Solanaceae, which includes both edible and toxic species. Common examples include tomatoes, potatoes, and bell peppers, which are safe to eat, while others like belladonna are highly poisonous. These plants are characterized by their distinctive flowers and fruit, often containing alkaloids that can be harmful. While many nightshades are staples in diets around the world, some individuals may experience sensitivities to them, leading to discussions about their health effects and dietary implications.