You may have an automation that you only want to run for certain groups of contacts. For instance, you may have an automation that applies only to contacts who are already customers, who have already viewed a certain page of your website, or haven’t opened a specific email.
You are able to specify which contacts you want to enter an automation by creating a segment. You can access this option when you add a triggering condition or by clicking a triggering condition (after it’s already been added).
After clicking the checkbox highlighted above, the segment builder will appear allowing you to specify what conditions a contact must match in order for the automation to begin. A contact that does not match those conditions will not enter the automation.