Tomato Purée (in the U.S.) is a thick sauce made from cooked then strained tomatoes. Tomato puree is thinner than tomato paste but thicker and more flavorful than tomato sauce. Tomato sauce has salt and other seasonings added.
Some tomato canning companies pack their whole or chopped tomatoes in tomato puree rather than juice.
In the U.K, tomato puree is what we refer to as tomato paste in the U.S.
You can easily make your own substitute for tomato puree: