This is the 8596th most frequent Russian word.
ольги
"Ольги" is the genitive singular or nominative plural form of the Russian female name "Ольга" (Olga).
In this sentence, 'Ольги' is the genitive form of the proper noun 'Ольга', used to indicate possession or relation.
Я купил книгу для Ольги.
I bought a book for Olga.
Here, 'Ольги' is in the genitive case and used to denote origin or source.
Этот подарок от Ольги.
This gift is from Olga.
In this instance, 'Ольги' is the genitive case, expressing possession (interests belonging to Olga).