In terms of the number of words, it is called: seven words, also called seven-character poem. (that is, seven words per sentence)
Syntactically, it is called quatrains, and this seven-character quatrains is called seven-character quatrains.
Quatrains, also called truncated sentences, broken sentences and quatrains, are short and pithy. It is a popular genre of Chinese poetry in the Tang Dynasty and belongs to a form of modern poetry.