At 8:59:58 the software knows that the news ends in two seconds, that a five-second ident follows, and that the film after it starts on frame one at 9:00:05. It cues the file, crossfades, keeps the logo in the corner, fires an SCTE-35 cue thirty seconds before the first break, and does this again every few minutes until the schedule runs out, at which point it fills from the library rather than going to black. The cloud playout guide breaks the job into its four parts; this page is about how that job is bought.
What it is not is live-production software. A vision mixer or a desktop switcher takes cameras and sources and makes a programme; playout takes finished programmes and makes a channel. Many channels use both, and the seam between them is a live input the schedule switches to at the right time and back from when the show ends.