Tomato Purée is made either from the liquid obtained from crushed tomatoes, or from the fleshy parts leftover after tomatoes are prepared for other uses such as Tomato Juice.
It is concentrated until it is thick, though it is not meant to get quite as thick as Tomato Paste.
You can, however, pretty much use Tomato Purée and Tomato Paste interchangeably without worry.
Often comes in tubes.
Ketchup; Tomato Paste
½ cup (125 ml / 4 oz) tomato purée = 1 tablespoon powdered tomato (Source: So Easy to Preserve, 2014, page 364.)