They mean "an animal" in the cladographic sense as being part of the same evolutionary tree as modern animals, and not e.g. lichens or funguses. Specifically, they seem to have detected cholesterol (or some decay product thereof maybe) in the fossil, which is a lipid that only animals make.
The identity of the ediacaran fauna has long been controversial. They don't "look like" modern animals (all of whom descend from forms that appeared later, in the cambrian explosion), so they're hard to place. This is a big, big result if it holds up.
The identity of the ediacaran fauna has long been controversial. They don't "look like" modern animals (all of whom descend from forms that appeared later, in the cambrian explosion), so they're hard to place. This is a big, big result if it holds up.
FWIW: this is the Wikipedia article you want to be reading: https://en.wikipedia.org/wiki/Ediacaran_biota