In Vietnamese, the adjectives (Vietnamese: Tính từ) always come right after the nouns they modify:

áo đỏ

red shirt (literally: "shirt red")

They always say about the particular trait, the property of the noun (before it). They can have the "phó từ" (like the adverbs in English) before it (e.g:"đã" for the sentence in the past simple tense, "sẽ" for the sentence in the future simple tense, "đang" for the sentence in the present progressive tense,... for more, see Tense)

Lúc này, thành phố đang rất yên tĩnh.

Now, the city is very quiet. (in present progressive tense)

The adjectives can separate to two main kind:

• The adjectives mean the relative particular trait: They can go with "rất" (very), "hơi" (quite), etc.
• The adjectives mean the absolute particular trait: They can't go with "rất", "hơi", etc.