This is the 27th most frequent Russian word.
ее
"Her" or "hers."
The word 'её' stands for 'her' as a direct object pronoun for a female subject.
Я видел её в магазине.
I saw her in the store.
The word 'её' refers to possession ('her') of the idea.
Книга, которую мы читаем, её идея.
The book we are reading is her idea.
The word 'её' indicates a direct object, referring to a feminine inanimate noun mentioned in context.