I head it from someone, but I can't understand it.
Although found that in reddit: wtf_is_insert_select_mode , I don't have any idea still.
Could anyone explain it and give me some example?
Do you really want more than this, from :help vim-modes
?
Insert Select mode Entered when starting Select mode from Insert mode.
E.g., by dragging the mouse or <S-Right>.
When the Select mode ends, Vim returns to Insert mode.
If the 'showmode' option is on "-- (insert) SELECT --"
is shown at the bottom of the window.