This is the 8765th most frequent Japanese word.
木沢
"木沢" (Kizawa) is a Japanese surname or place name, typically meaning "tree" (木) and "marsh/stream" (沢).
In this sentence, 木沢 is being used as a proper noun, likely a surname of a person.
木沢さんは今日学校に来ました。
Mr. Kizawa came to school today.
Here, 木沢 refers to the name of a place that likely has a forest.
木沢の森はとても美しいです。
The forest of Kizawa is very beautiful.
This usage indicates that 木沢 is being identified as an individual's name.