What is the difference between Passata & Pasta Sauce?

Passata is just strained / sieved tomatoes, that is smooth, to use in recipes.
Pasta sauce is made with tomatoes, onions, herbs, garlic,seasoning to use with pasta in a dish, it can have cooked meat [ ground ] in it to enrich the dish.

Passata is uncooked tomato puree/paste. Pasta sauce has lots of other things in it, and is cooked.

Passata is made from uncooked tomatoes .. that have been crushed and sieved (to get rid of the skin and pips) to get a smooth sauce.
There is nothing else added.

Pasta sauce is made from cooked pureed tomatoes with added ingredients (garlic, herbs .. or whatever).

Passata is merely whole tomatoes pushed through a sieve or food mill. Pasta sauce is a misnomer as nearly anything can be a pasta sauce. I assume you are referring to a Marinara sauce, which is tomato based, unlike an Alfredo, which is cream based.

Passata is simply sieved tomatoes. They have been PASSED through a sieve - geddit? You can make your own - put tomatoes with the seeds and skins removed in a blender or food processor, whizz until it's smooth, and that's passata. You use it as a cooking ingredient. If you want tomato in what you're making, but not pieces of tomato, then use passata.

There is no such thing as "pasta sauce". Pasta goes with many things. Why on earth do people have this strange idea that "pasta sauce" means tomato? It certainly doesn't in, say, spaghetti alla carbonara. That's egg and bacon spaghetti with not a tomato in sight! But if you want tomato sauce with your pasta, passata could be one of the ingredients.

For example, I know a recipe for tagliatelle (or it could be spaghetti) and meatballs, and that includes tomato sauce. To make this sauce, the recipe says you start off with finely chopped onion and garlic (whizz it in a food processor) and fry that gently until soft with a little dried oregano, add passata, water, salt and pepper and a pinch of sugar, cook for 10 minutes, then add a little milk and cook for another 20 minutes. (Yes, Italians do put milk in it.)

If you're actually making this for meatballs, then put the meatballs in for that last 20 minutes and that will get them cooked too without needing another pan. So it's all going on in one pan and you just need another one to boil the pasta.

What I do to make this is I don't buy passata. While the onion, garlic and oregano are frying, I wash out the food processor and use it again to whizz up a can of chopped tomatoes. It's slightly cheaper than buying passata, and I get through a lot of canned tomatoes anyway for other dishes so why not use them for this too.

Passata is something you can use to MAKE pasta sauce, as one ingredient.

There are many different types of pasta sauces -- a standard Italian-American red sauce is only one -- but a red sauce like that can be made with passata, plus other ingredients.

Passata is a medium-thick, pourable, uncooked red tomato sauce made from crushed and strained tomatoes. It has almost the same consistency as tomato ketchup.

http://www.cooksinfo.com/passata

As a substitute I would try Contadina Tomato Puree since Contadina's is thick.

Pasta Sauce is a cooked sauce.

Passata is a tomato puree - cooked tomatoes are passed through a sieve to make a thick puree.
Pasta sauce (red sauce) is a tomato based sauce with seasoning, herbs, and often other vegetables in it (onions, garlic for example).