Same webpage show different content over time. The webpage is just a presentation of queried data. If data changes in the database, so does the webpage content.
Dynamic template is the same. It is a container for stored data, and based on timely-based queries.
You can for example, create an email template that always shows the latest product in your store.
When ever you send this template, it queries the database in real-time, pulls fresh date, and change its content.
A combination of dynamic templates with a repetitive campaign, can take your business marketing to a new level.
See a demonstration in the following video: