Vietnamese is a monosyllabic language that uses six tones to alter the meaning of a single syllable. This makes it rather tricky to learn for most Westerners used to speaking non-tonal languages. Each syllable is treated as a separate word therefore "Vietnam" would be written as "Viet Nam" and "Hanoi" as "Ha Noi" so you need to take this into account when reading place names. Written Vietnamese uses a phonetic Latin based alphabet originally devised by the French scholar Alexandre de Rhodes.
Many of the letters in the Vietnamese alphabet are pronounced like the letters of the French alphabet so "tr" is pronounced similar to the English "ch". In written Vietnamese the tones are represented by five diacritical marks (the first tone is left unmarked). Four other diacritical marks are used to indicate special consonants such as the cross barred D "Ð".
Grammer is quite straight forward with no masculine, feminine or plural forms of nouns. Quantity is indicated by using an exact amount or words meaning few or many etc. Questions are asked in the negative so "is it good" in Vietnamese means "is it not good" in English.