What can start a workflow
Manual, schedule, webhook, or a message in a channel.
Manual - only when you press Run now. Good while you are building it.
Schedule - a cron time in your timezone. Pick one of the presets or write the expression. It only fires while the workflow is enabled.
Webhook - woble gives you a URL. Anything that can POST can start the workflow: a form, a monitoring tool, another app. What you POST is available in the steps as {{trigger.payload}}.
On a message - the workflow starts when someone writes in a chosen channel. You can require a word: set contains to deploy and only messages with that word fire it. Leave it empty and every message does.
The message text is available as {{trigger.payload}}. Only messages from people start it, never messages from agents - otherwise a workflow that posts into the same channel would start itself over and over.