What’s the difference between persist, save, merge and update? Which one should you use?

1.Hibernate: save, persist, update, merge, saveOrUpdate ：https://www.baeldung.com/hibernate-save-persist-update-merge-saveorupdate
2.What’s the difference between persist, save, merge and update? Which one should you use? https://thorben-janssen.com/persist-save-merge-saveorupdate-whats-difference-one-use/
其中https://www.youtube.com/watch?v=SH29O-bcQlc 视频讲解
3.https://techblog.bozho.net/how-does-merge-work-in-jpa-and-hibernate/