A five-day split training one muscle group per session, so chest, back, shoulders, arms and legs each get one day a week.
It is the classic bodybuilding-magazine layout and it is unfairly maligned. Once weekly frequency per muscle is not optimal, but total weekly volume is what drives most of hypertrophy, and if a client hits 15 to 20 hard sets for chest on Monday they will grow.
The real problems are practical. Twenty sets in one session means the last five are done tired, which is where junk volume lives. And missing Thursday means the shoulders get nothing for two weeks.
Use it with clients who train five days reliably, enjoy long sessions on one muscle, and are past the beginner stage. For everyone else, an upper/lower or PPL split gets the same volume at twice the frequency.