My friend says that thin pizza crust is nothing but a cracker, but I think there are significant differences between the two products. For example, if you buy a store-bought cracker and add pizza sauce, toppings, and cheese to it, you won't get anything remotely like a pizza.
tl;dr: where do the ideas of pizza crust and cracker diverge?
Best Answer
Two factors:
Leavening: pizza crust is generally made with a leavened, yeasted dough, that has risen for a hour or more before rolling out. Crackers are generally made with a "short" dough, which contains no leavening at all or only a tiny amount of chemical leavening. Even crackers that are made with a yeasted dough (e.g. sourdough crackers) are not given a long time to rise.
Texture: crackers are generally supposed to, well, crack. They should be crisp, crunchy, and/or flaky. Whereas pizza dough is supposed to be chewy and/or bready, and certainly not crunchy.
Now, there's obviously some room for overlap here. For example, if I roll out a sourdough pizza crust really thin and top it only with salt, and bake it until crunchy, it's not going to be particularly different from a sourdough cracker. However, most pizza crusts are very different from most crackers.
Hope that helps!