According to google, it means tomato paste, passata means 'passed' as the tomatoes have passed through a sieve to remove seeds etc.

Actually passata is not tomato paste but the larger bottles/jars of something similar, often it's just called pasta sauce.  if you read the labels it's not hard to find one that has just tomatoes in the ingredients, maybe a little salt as well.  I use it a lot now to make things like bolognese sauce for spaghetti and often add it to other things eg soups and casseroles.

 

passata is just pureed tomatoes

I would imagine you'd have to sieve it to get rid of seeds and skin, crushed tomatoes or tinned tomatoes would do the same thing although the texture wouldn't be the same.

I make my own. I just get a bunch of tomatoes and cook them down slowly for hours. You know you're done when it looks, smells and taste like the paste you buy. I don't skin or seed them...too lazy. I was so amazed at the result, and so easy too. Then if I want tomato sauce/ketchup I just whiz up and add a bit of salt. The skins and seeds just seem to disappear. It's so yummy! Didn't have to add anything else for my taste. You can add what you like to make it what you like. It's not the right time of year to buy them in bulk, but I'm going to grow some this year. Haven't done that in ages.