Formalism Texts - "On Realism in Art" by Roman Jakobson (1921)

Jakobson tries to define that vague, magical thing, "literariness," which he says is the true object of literary "science." Isn't that some kind of oxymoron?

First thing's first. What is the difference between "literature" and "literariness"?

Second thing's second. According to Jakobson, why is it so important to focus on "literariness"?