This is the 1381st most frequent Russian word.
абсолютно
"Absolutely" or "completely."
In this sentence, 'абсолютно' is used to emphasize the impossibility of the situation, functioning as an adverb to enhance the adjective 'невозможно' (impossible).
Это абсолютно невозможно.
It is absolutely impossible.
Here, 'абсолютно' reinforces the adjective 'уверена' (confident), indicating the certainty of her confidence.
Она абсолютно уверена в своём выборе.
She is absolutely confident in her choice.
In this context, 'абсолютно' modifies the verb 'понимаю' (understand), serving as an intensifier to express complete lack of understanding.