my favorite food is pizza
Mmm. I love pizza. I am from the NY metro area and am a pizza snob. lol The word pizza was first documented in AD 997. Didn't realize it was that old. 
was it originally from Italy?
No, it wasn't. The precursor of pizza was more then likely the focaccia. It was a flat break known to the Romans as "panis focacius.". Toppings were then added to it. 
so what makes a pizza a pizza :)
It was in the late 18th century when tomato was added to the focaccia in Naples.
I like a simple thin crust cheese pizza
So do I. The cheese on pizza encompasses several varieties of cheeses.  
forget about the deep pan pizza, that is not even pizza :)
Deep Pan Pizza
Deep Pan Pizza was a chain of British pizza restaurants, that was best known for its "all you can eat" business model.
At the time its closure was announced in March 1998, there were 89 Deep Pan Pizza restaurants in the UK. The owner of the chain was City Centre Restaurants, and James Naylor City Centre's chief executive (CEO), said, "The brand was becoming dated. Thin crust pizzas are becoming more popular, with fewer people eating deep pan."
History of pizza
The history of pizza begins in antiquity, when various ancient cultures produced basic flatbreads with several toppings.
A precursor of pizza was probably the focaccia, a flat bread known to the Romans as , to which toppings were then added. Modern pizza developed in Naples when tomato was added to the focaccia in the late 18th century.
The word "pizza" was first documented in 997 A.D. in Gaeta and successively in different parts of Central and Southern Italy. Pizza was mainly eaten in Italy and