Google introduced dynamic email for Gmail on the web in March of this year, with a rollout beginning in July. The feature utilizes AMP to provide more interactivity within emails. It was noted at the introduction that mobile support would soon follow, and hints of the feature were found in the APK as far back as January. It seems, almost a year later, that "soon" has arrived: Google is beginning an extended rollout of dynamic emails on the Android and iOS apps today.
Dynamic email allows you to access web functions from within messages, so you can interact without ever leaving Gmail. You can drop a comment or check on your shipping status and scroll right to your next email. AMP allows the content of your messages to stay up to date, as well, so when you open an email you can see the most recent status of your orders or postings.
Dynamic emails let users engage with message content right in the Gmail app
The rollout of dynamic emails has started for both Android and iOS users, but may take a few weeks or more to come to your account. You should notice when you get it, though, as dynamic emails will be turned on by default.