This is the 1645th most frequent Russian word.
елена
"Елена" is a Russian female given name, equivalent to "Elena" or "Helen" in English.
Here, 'Елена' is used as a proper noun referring to a person's name.
Елена любила гулять в парке.
Elena loved walking in the park.
In this sentence, 'Елена' is again a proper noun being used to introduce or refer to the individual's name.
Ею звали Елена, и она была доброй.
Her name was Elena, and she was kind.
'Елене' is the dative case of 'Елена', showing that the book was given to her.