The tomato is a plant in the Solanaceae or nightshade family. Originating in South America, the tomato (Lycopersicon lycopersicum and L. esculentum) is now grown world-wide for its brightly coloured (usually red, from the pigment lycopene) edible fruits. The word "tomato" is of Nahuatl origin.
Lingering doubts about the safety of the tomato were supposedly put to rest in 1820, when Colonel Robert Gibbon Johnson announced that at noon on September 28, he would eat a bushel of tomatoes in front of the Salem, Massachusetts courthouse. Purportedly, an immense crowd of more than 2,000 persons gathered in front of the courthouse to watch the poor man die after eating the poisonous fruits, and were shocked when he lived.
This misapprehension has been banished, and tomatoes are now eaten freely in Europe as well as the rest of the world. In the past it has also periodically been esteemed as a purported aphrodisiac; today, its consumption is believed to benefit the heart.
Botanically a berry, the tomato is generally thought of--and used--as a vegetable: it's more likely to be part of a sauce or a salad than eaten whole as a snack, let alone as part of a dessert (though, depending on the variety, they can be quite sweet, especially roasted).
Used extensively in most Mediterranean cuisines, especially Italian ones. The tomato has an acidic property that is used to bring out other flavors.
The reputation of tomatoes has been severely damaged by their appearance in the "Killer Tomatoes" movies. More on IMDB.