When does the default deploy workflow get called?

In the documentation (Default Workflows | Bitrise DevCenter) it mentions the default deploy workflow that gets created for new apps and that it produces artifacts.

When does this workflow (if ever) get called? Does this get called when another workflow runs to produce the artifacts for it or does it need to be explicitly called as its own workflow?

Hello,

As you mentioned, the deploy workflow gets created along with the primary workflow when you add an application. These 2 workflows are just basic workflows that are generated based on the analysis of your app when it is added to Bitrise. Like any workflow, it can be triggered manually, via a webhook/trigger map, by the Bitrise Build Start step, or with an API call.