This is the 309th most frequent Russian word.
написал
"Wrote."
Here, 'написал' is used in the past tense to indicate the completion of the action of writing by a male subject (as inferred from the masculine verb ending).
Я написал письмо.
I wrote a letter.
In this example, 'написала' is the feminine past form of 'написать,' reflecting the feminine subject.
Она написала статью для журнала.
She wrote an article for a magazine.
This sentence uses 'написал' in a question to inquire about the author of the book. The form 'написал' implies the question assumes a masculine author or is used in a neutral sense.