Critic speak is tough, but we've got you covered.
Quote :"On the Sounds of Poetic Language"
The phenomena of language must be classified from the point of view of the speaker's particular purpose as he forms his own linguistic pattern. If the pattern is formed for the purely practical purpose of communication, then we are dealing with a system of practical language (the language of thought) in which the linguistic pattern (sounds, morphological features, etc.) have no independent value and are merely a means of communication. But other linguistic systems, systems in which the practical purpose is in the background (although not entirely hidden) are conceivable; they exist, and their linguistic patterns acquire independent value.
First thing's first: don't get Jakobson confused with Jakubinsky. One is a "son" and one is a "sky." One is way famous in lots of branches of literary theory and the other is only sort of within the nearly dead branch of Formalism. Just cuz they both start in "Jak" doesn't mean they're equally jacked up in the theory world.
That said, they believe in basically the same stuff. There are two types of language: practical and poetic language. Practical language is all about communication. If we're sitting at dinner, and I want to spice up my bland chicken, and I ask you, "Pass me the salt," that's practical language. The words serve one purpose: to communicate something we want or need.
On the other hand, if we're sitting at dinner and I burst into song, chanting, "Puh-lease puh-paasss me the sweet yummy tasty salty-salt, you friend full of wonder and enchantment," that's poetic language (well, more or less).
Sure, maybe we do actually want the salt. But there's a lot more going on here than just practical communication. We're playing with language. We're alliterating. We're adding more information than is necessary. Not to mention syllables. The words and sounds aren't just there to communicate our need for salt—they're doing tons more than that. Got it?
Jakubinsky's distinction between practical and poetic language was super important for the Formalists. This was the first time that someone had actually tried to explain how language is used differently in a literary or poetic context.
And yes, while we may all know there's a difference between everyday speech and poetic speech, however salty that speech may be, no one had done such a good job of explaining the difference between the two until Jakubinsky came along.