I’m a bit confused with known words and hibernation.
If i mark a word and choose to add it to “known words” does it mean i essentially burned it and it’s not gonna ever appear in any of my reviews? Or does that mean i just skipped lesson for it and i’ll still get it in reviews?
Because if it’s still gonna appear then i guess burning it is only possible with “hibernate”?
No, adding ‘known’ adds it as a known tag. This known tag can then be used for deck filtering, namely to hibernate ‘known’ content so it doesn’t show up in lessons or reviews. This has no equivalence to SRS level or ‘burning’. On a side note, you can customize your SRS level on any item but that is separate feature.
If you don’t want to study it, use the hibernate status and it will not show up in lessons or reviews.
I see, thank you. By the way, is there an option to remove words from “known words” list?
I think this feature is coming fairly soon. For now I’ve seen users send requests to the team to manually reset their known base in this thread:
Yep! High on the priority list for upcoming features! 
If you need it to be cleared feel free to reply here or in that other thread first.
As @s1212z mentioned, known words is “just” a visual marker to see which cards you already know in other decks and filter those by hibernating them when needed.
Hibernating a card suspends it indefinitely so it does not show up in your lessons and reviews.