Refers to a person who has graduated from a university, especially with a bachelor's degree. Often used in formal or academic contexts.
He is a graduate of the University of Tokyo.
学士の資格を持って就職活動をする。
I job-hunt with a bachelor's qualification.
bachelor's degree
The degree itself, as in 学士号. Often used in educational or credential contexts.
彼女は経済学の学士を取得した。
She earned a bachelor's degree in economics.
He earned a bachelor's degree in economics last year.
学士 refers specifically to a bachelor's degree, whereas 学位 is the general term covering bachelor's, master's, and doctoral degrees alike.
学士 is a bachelor's degree, one level below 修士, and the two are easily confused when learning academic titles.
admission of university graduates to an undergraduate program