This is the 1256th most frequent Russian word.
письма
"Письма" means "letters" (as in written correspondence) in English.
The word "письма" is in the accusative plural form and refers to letters as written communications.
Я получил вчера два письма от своих друзей.
I received two letters from my friends yesterday.
Here, "письма" is in the nominative plural form and acts as the subject of the sentence, referring to written letters.
Письма, которые вы отправляете, всегда интересны.
The letters you send are always interesting.
In this sentence, "письма" is in the nominative plural form, referring to multiple written letters.