As per Zendesk:
Automations are similar to triggers because both define conditions and actions that modify ticket properties and optionally send email notifications to customers and agents. Where they differ is that automations execute when a time event occurs after a ticket property was set or updated, rather than immediately after a ticket is created or updated.
The simpler way to think of it is automations are triggers that do not run instantly. They are time based than event based.
Instead of managing Zendesk automations via Zendesk itself, we instead use GitLab itself via the zendesk-automations project. This allows us to have version-controlled automations. For more information on managing Zendesk via the various GitLab projects, please review Using the sync repos.
As we have many automations, and they change quite frequently, the best resource to see all the current triggers would be the zendesk-automations project.