By default, pop-up events don’t appear in your Google Analytics. For example if you want to measure and analyse how users behave after they have been served a pop-up and additionally if they have retrieved a discount code, you need to add separate event tracking and goal setup between your pop-up and Google Analytics.
How Google describes event tracking: “Events are user interactions with content that can be tracked independently from a web page or a screen load. Downloads, mobile ad clicks, gadgets, Flash elements, AJAX embedded elements, and video plays are all examples of actions you might want to track as Events.”