Telex (or TELEX) is a Vietnamese typing method in the form of unmarked by the Vietnamese telegram signal, when entering text into a computer from an international keyboard. This typing method is based on a convention of Vietnamese language expression on telex, called telex convention. Wikipedia
VIQR (short for Vietnamese Quoted-Readable), also known as Vietnet is a convention to write Vietnamese letters using 7-bit ASCII encoding. Because of its convenience, this convention is commonly used on the Internet, especially when Unicode encoding has not been widely applied. Currently, VIQR convention is still used by some people or letter groups.Wikipedia
VNI is one of the conventions for entering Vietnamese from the international keyboard into text on the computer by typing the number after the letter. Wikipedia