Is there a difference between coca, focaccia and pizza?

As you know, focaccia and pizza are Italian dishes, and coca is Catalonian (a region at Spain's northeast). They all have toppings, and similar doughs (with wheat flour and yeast).

Classical focaccias:

• Are thicker than [Italian] pizzas (about 3˜4 cm (1.2˜1.6 in) thick)
• Have rectangular shape
• Have herbs, salt and olive oil as topping
• Are baked for about 20 minutes.

Italian pizzas:

• Are thin (less than 5 mm (0.2 in)) except their outer part
• Are round (see notes below)
• Have many different toppings, almost always including cheese, and most of the times tomato sauce or whole tomato
• Are baked for about 90 seconds (this is very important for italian pizzas)

Cocas:

• Can be as thick as focaccias or as pizzas, usually depending on the topping.
• Are either rectangular like focaccias, or really long shaped like these ones from Barcelona.
• Can be either sweet or salty.
  • Sweet ones are usually thin as pizzas, always having sugar as topping and maybe pinnions, candied/confited fruit and/or anis (it might remind you to a Spanish Roscón de Reyes).
  • Salty are just a bit thicker than pizzas, and may have many ingrediets, but never cheese or any sauce: usually onions, green/red pepper, eggplant, cooking chorizo, blackpudding, butifarra, olives, hardboiled eggs, etc.
• Are baked for 30 to 45 minutes (aprox) (which is, in my opinion, their biggest distinction with pizzas)

Notes: I know there are some pizzas in America that do not fit in the description I gave. But I understand your question is focusing on Italian pizzas.

Also, sure there are pizza al taglio in italy, but despite having different shapes and cooking time than pizza pizza, they share the same Italian spirit, and can be noticed different different to cocas.

You can make the three of them with natural yeasts, like sourdough/lievito naturale/massa mare, but certainly not with chemical rising agents.

First of all is coca a Spanish dish with huge variety. A coca can just as well be made of thin yeast dough with savory topping (similar to an Italian pizza but not necessarily with cheese) as well as sponge-cake-like (leavened just with the beaten eggs or with baking soda) with sweet topping.

Foccacia also comes in many varieties, but typical foccacia is made of yeast dough, about one inch thick, which is sprinkled with olive oil and herbs before baking. Foccacia can also be made thinner and without yeast, but that makes a much crispier bread. It may be topped with other ingredients, but does not have to and if it is topped, it is mostly only a simple topping like olives, onions or cheese. It is usually not eaten alone, but as a side dish. Here is a typical foccacia, topped with black olives.

Pizza dough is very similar to foccacia, but in Italy, a pizza is always much thinner. The thick American style pizza is not common in Italy. Except for the thickness, the difference between foccacia and pizza is much more in the topping. A pizza is almost always topped with at least tomatoes or tomato sauce and cheese and mostly with other savory ingredients.

In some regions, focaccia is referred to as pizza, and vice versa. Then focaccia comes in several forms. There's the traditional focaccia, which is a yeast dough, there is focaccia di recco (or al formaggio) which consists of a non yeast dough but is rolled out very flat and filled with prescinseûa, a ligurian fresh cheese) and there is a double baked focaccia, which is a baking powder dough. I would advise the books of Fred Plotkin, and especially this one: http://www.amazon.com/Recipes-Paradise-Life-Italian-Riviera/dp/0316710717/ref=la_B0034P0YQI_1_10?ie=UTF8&qid=1351975671&sr=1-10 for more information and classic recipies