Kaishu is the Chinese calligraphy script also called the “regular script.” The name refers to a standardized, clearly structured form in which characters have balanced proportions and recognizable strokes.
Regular script developed from earlier clerical and semi-cursive styles and became established during the late Han and Three Kingdoms periods. It matured during the Tang dynasty, when calligraphers such as Yan Zhenqing and Ouyang Xun helped define influential models.
Kaishu remains the usual script for learning Chinese characters, formal handwriting, inscriptions, printed type, and educational materials. Its strokes are written separately and deliberately, making the character structure easier to study than in cursive writing.
The other choices are different script categories. Cao shu is cursive script, lishu is clerical script, and zhuanshu is seal script. Calligraphy traditions often compare scripts by stroke order, degree of abbreviation, and the freedom allowed in connecting strokes.