Nachos are a dish that originates from Northern Mexico.  
What are in nachos?
It is a dish with tortilla chips and it is covered in cheese.  It is typically a snack food
What kind of cheese is it covered in?
Cheeses of Mexico
Cheeses in Mexico have a history that begins with the Spanish conquest, as dairy products were unknown in pre-Columbian Mesoamerica. The Spanish brought dairy animals, such as cattle, sheep, and goats, as well as cheesemaking techniques. Over the colonial period, cheesemaking was modified to suit the mixed European and indigenous tastes of the inhabitants of New Spain, varying by region. This blending and variations have given rise to a number of varieties of Mexican cheeses. These are most popular in the country,
Nachos
Nachos is a Tex-Mex dish from northern Mexico that consists of heated tortilla chips or "totopos" covered with melted cheese (or a cheese-based sauce), often served as a snack or appetizer. More elaborate versions of the dish add other ingredients, and may be substantial enough to serve as a main dish. Ignacio "Nacho" Anaya is credited with creating the dish around 1943; the original nachos consisted of fried corn tortilla chips covered with melted cheese and sliced jalapeño peppers.
History.