This construction is the adjective sentence. Adjectives describe characteristics, appearance, or conditions of the noun. In Japanese, there are two kinds of adjectives, namely, い-けいようし or i-adjective (Ａ(い)) and な-けいようし or na-adjective(Ａ(な)). I-adjectives are introduced in this lesson.
あの さかなは あたらしいです。
That fish is fresh.
See the index of 『初級日本語』(Shokyuu Nihongo) for all the i-adjectives presented in the books.
Lesson 6-9: Na-adjectives「これは きれいな はなです。」
These flowers are pretty.