This is the 7623rd most frequent Russian word.
ерина
"Ерина" is not a standard Russian word; it might be a proper noun (e.g., a name) or a misspelling.
Ерина here is a proper noun and represents someone's name, used as the subject of the sentence.
Ерина готовится к экзамену, стараясь выучить как можно больше.
Erina is preparing for the exam, trying to learn as much as possible.
Ерина functions as a proper noun being the title of a book.
На полке стояла книга с титульным названием 'Ерина'.
On the shelf stood a book with the title 'Erina'.
Ерина is used as a proper noun and brand name in this context.