A trigger fires on a record being created or updated, a field hitting a certain value, a scheduled time, or someone clicking a button on a record. From there, actions can send an email, update or create another record, post to a webhook, or send a message to another connected app. For anyone comfortable with a little JavaScript, the Scripting extension inside Automations opens up logic the point-and-click builder can't express on its own, conditional branching, looping over multiple records, custom formatting.
For logic that starts and ends inside one base, triggered by things happening inside Airtable itself, this native layer covers a lot of ground without needing a developer at all.