There are so many different aspects by which flour can be defined that most online descriptions of it remind me of the old story about the 7 blind men and the elephant: Each blind man was accurately describing one important part of the elephant, but none of them were describing the whole elephant.
For the last several weeks I've been reading Wheat Flour Milling by Posner & Hibbs, the standard textbook on the subject, and though I'm only 2 chapters in, I'm already pretty overwhelmed by all the material. (People can and do earn PhDs in flour milling.)
I'm probably going to write an article (possibly several) on what I've learned later this fall, so I won't go into it in depth at this time.
As I understand it at this point, type 00 flour describes the granularity of the flour, ie, how finely ground it is. That doesn't tell you what kind of wheat it came from, what protein levels that wheat has or how much of the bran and germ are still left in the flour, and those are all things that affect how the flour will perform in various types of baking. (There can be other factors as well, such as how the flour has been treated before or after milling.)
Basically, Italian flours come in Type 0, Type 00 and Type 000, the more zeroes, the finer the grind. Type 0 is a coarse flour, type 00 is probably fairly close to most American AP flours for grind (though some sources say it is a bit finer than the average American AP flour, more like 'southern' flours such as White Lily), and type 000 is very finely ground, the closest equivalent in the USA is probably cake flour.
Different brands of Italian 00 flour will be made from different types of wheat, and that will affect how the flour performs in various types of baking.
The suitability of Caputo Type 00 flour for pizza, which it is how sources like Amazon may label it for marketing purposes, is an entirely separate matter. If you follow the discussions on pizza-oriented forums like Peter Reinhart's Pizza Quest, you will find some people who insist that you must use a very high protein content flour for pizza and others who insist that you should use a lower-than-average protein content flour. Both factions have valid arguments for their points of view, but that's because they have different opinions as to what pizza crust 'should' be.
Peter Reinhart's book American Pie gives a number of different crust recipes, from various types of pizza across the USA and around the world, and calling for various types of flour. I've tried several of them, and I have to say they were ALL delicious!
