Catch-up is a type of VOD (Video On Demand). Catch-up can often be considered of recording your TV in some sort so that you can catch-up anything you missed at a later point. Most IPTV services provide some sort of catch-up option, with a limited timeline.
Technically, you can “rewind” what was a straight broadcast and then start viewing from any point. After viewing your missed TV program, you might be capable to jump over to another TV program.
Catch up service is only available on the channels that are marked with the orange clock icon on MAG just like the below image.