This is the 1663rd most frequent Russian word.
ольга
Olga: A female given name in Russian.
Here, 'Ольга' is used as a proper noun, representing a person's name, and serves as the subject of the sentence.
Ольга читает книгу.
Olga is reading a book.
In this sentence, 'Ольге' is the dative case form of the name 'Ольга', indicating to whom the book was given.
Я дал книгу Ольге.
I gave the book to Olga.
Here, 'Ольге' is the prepositional case form of 'Ольга', functioning to express possession or association.