It means who writes the letter in English.
Who's writing the letter.
Who do you frequently write letters to?
Quien te dijo como escribir esto = Who told you how to write this?
"who's the letter from?"
"De quien" means from who?; "De quien(?)-whose(?)";
"Con quien estas" translates to "who are you with" in English.
Se escribe con you con acento
Escribe means 'he writes'
"De quien" means "from whom"
"Hola quien eres" translates to "hello who are you" in English.
"Quien cumple años" in English means "who is having a birthday."
"Y esa quien esss" in English translates to "And who is that?"