Catch-up TV lets you watch a programme that has already aired, well after its original broadcast slot — no recording required, and no need to have been watching live in the first place.
Behind the scenes, the provider retains a rolling window of every channel’s output — commonly somewhere between 24 hours and a full week depending on the service — and lets you scrub back through that window exactly like browsing an on-demand library. Open the guide, pick a time earlier in the day or week, and playback starts from that point.
This is different from a traditional recording in one useful way: you do not need to remember to set anything in advance. If a friend mentions a programme the next morning, there is a good chance it is still sitting in the catch-up window waiting to be watched, with no setup required beforehand.
Combined with a large on-demand VOD library, catch-up effectively removes the idea of ‘missing’ a broadcast altogether — the schedule becomes a suggestion rather than a deadline.