When two versions of one email address are sent against each other, it is called A/B Split. A/B Split or Split Testing is a testing tactic that helps evaluate the version with the higher performance by measuring the feedback against KPIs like clicks, opens, and others.
The complexity of A/B testing differs. Simple A/B tests involve sending multiple subject lines to test the one with the highest number of opens. The more advanced A/B testing involves testing distinct email templates against each other to identify the template with the highest click-throughs. Therefore, a reliable method of boosting the open and click-through rates of your emails is to subject your campaigns to A/B testing.