History of writing in Vietnam
Written Vietnamese today uses the Latin script-based Vietnamese alphabet to represent native Vietnamese words (thuần Việt), Vietnamese words which are of Chinese origin (Hán-Việt, or Sino-Vietnamese), and other foreign loanwords. Historically, Vietnamese literature was written by scholars using a combination of Chinese characters (Hán) and original Vietnamese characters (Nôm).
Source: Wikipedia — History of writing in Vietnam (CC BY-SA 4.0)