A city is larger than a town. New York City, Boston, Miami, and Los Angeles are examples of cities. All state or country capitals are cities; cities usually have some significant political, economic or cultural importance. The word town refers to a smaller population center. And a very small population center - even smaller than a town - is called a village.
To complicate things, the central part of a city (especially the main commercial or business area) is called downtown. If you live downtown, you live right in the middle of the main action of the city - and it's more expensive to live downtown than to live in one of the other neighborhoods.
The dark, richly colored varieties of lettuce such as dark green, red or purple ones are the richest in nutritional value indicated by the presence of vitamin A and other antioxidants such as carotenoids and lutein, which is why it is considered as one of the worlds most popular vegetables.