A live feed is external data pulled onto a screen automatically (prices, stock levels, weather, departures, queue numbers), so what appears changes without anyone touching the content. The screen renders a template; the feed fills it.
This is where signage stops being a slideshow. A menu board that hides sold-out items, a transport display that reflects the actual next train, a factory board showing today's real output: each stays correct with no human in the loop, which is the only way accuracy survives across hundreds of sites.
The caveat is that a feed can fail in a way a static asset cannot: it can succeed and be wrong. If the source goes stale, the screen confidently shows yesterday's price. Every feed needs a defined behaviour for missing, stale and malformed data, usually a maximum age after which the zone hides itself rather than displaying something false. A blank panel is embarrassing; a wrong price is a customer dispute.
Second, the network the screens sit on rarely has the same uptime as the system publishing the data. Cache the last good value locally and decide deliberately how long it stays valid.