Dynamic messaging changes what a screen says according to context rather than playing a fixed sequence. The trigger might be time of day, the weather, stock levels, a queue length, or which store the screen is in.
It works because relevance is what buys attention in a place people are not choosing to look. A coffee promotion at 8am and a wine promotion at 6pm from the same template outperform a single all-day message without any extra creative work.
The caveat is that dynamic and personalised are different things, and the second is much harder to justify in public. Changing by time or weather uses no personal data at all. Changing by who is standing there does, and that shifts the deployment into consent and biometric territory. Most of the measurable gain comes from the first kind.
Design the fallback first. Every dynamic rule needs a defined default for when its data is unavailable, or the eventual failure is a screen with a gap where the message was.