A single rule, like “weekdays, 9 to 5”, covers most needs. But a schedule is never limited to one rule, and that is where it gets interesting.
You can give a playlist as many rules as you need and combine them with plain logic: play when all of the conditions hold, or when any of them do. That choice between all and any is the and/or logic behind a schedule, and it lets one playlist follow a pattern that no single window could describe.
As many rules as you need
Each rule is a condition: a window of time, a set of weekdays, a range of dates. Stack several with “all” and you narrow things down to an exact slice. Switch to “any” and you widen back out, covering several separate cases from one schedule.
A playlist could run across two unrelated campaign periods, a week in March and a week in September, and stay dark in between. Two date ranges, joined with “any”, on the same playlist.
Different times on different days
Because rules combine, the same playlist can behave differently from one day to the next. You might want it from 7 to 9 in the morning on weekdays, but 10 to 4 on weekends, all from one schedule.
You group the conditions for this. One group reads “weekdays and early morning”, another reads “weekends and midday”, and the playlist plays when either group is satisfied. The grouping is what keeps the two patterns from bleeding into each other.
Why it is worth knowing
Most screens never need this much, and a plain time window is enough. But when a screen has to follow a real rhythm, a building that opens at different hours on different days, or a campaign that runs in separate bursts, the schedule can keep up. You describe the pattern as rules, and the screen follows it on its own, with no one switching anything by hand.