This is the 1354th most frequent Russian word.
анатолий
"Анатолий" is a Russian male given name, equivalent to "Anatoly" in English.
The name 'Анатолий' is used here as a proper noun to refer to a person who is performing the action of going to the store.
Анатолий идет в магазин.
Anatoliy is going to the store.
The name 'Анатолий' functions in the instrumental case 'Анатолием,' indicating the agent who performed the action of writing.
Этот рассказ был написан Анатолием.
This story was written by Anatoliy.
Here 'Анатолиев' is used in the plural genitive case to indicate a group of individuals named Anatoliy, describing their attribute of creativity.