Google says this extension will show automatically on eligible ads when the landing page has a matching category for a search. The snippets can display additional details about the content found on the landing page for the ad, like specific brands or subcategories.
They can display with other extensions, though if Google finds that other extensions perform better than structured snippets, they’ll be more likely to appear with your ad instead.
Some dynamic structured snippets performance data will be available from the automated extensions report from the Ad extensions tab.
Advertisers can fill out a form to opt out of dynamic structured snippets, but Google emphasizes that automated extensions are a factor in Ad Rank.