Almost all people in Vietnam speak Vietnamese language (tiếng Việt). This is the official language of the country.  The majority of Vietnamese population (around 90%) speaks this language as native, however, the other 10% only speak Vietnamese as a second language. Vietnam is an ethnically diverse country, and it has various minority groups, each minority group speaks their own, and distinct from others, language. From the linguistic point of view, most of these minority languages are not related to Vietnamese at all. 

As the result of Vietnamese immigration, Vietnamese speakers are found throughout the world, notably in North America, Australia, Europe, and East and Southeast Asia. In the United States, Vietnamese is the sixth most spoken language. Vietnamese is the seventh most spoken language in Australia.

The Vietnamese alphabet (quốc ngữ) being used today is a Latin alphabet with additional diacritics for tones, and certain letters.

Learning Vietnamese at http://mylanguages.org/learn_vietnamese.php