The good news is that the social media platforms provide a lot of data about how your ads are delivered and how they perform. The bad news is that not everything they measure is important, and some important things are not being measured!
This is a complex subject. So, to keep things simple, we suggest you look first at the metrics that tell you about how much your ads have been exposed to the world; namely the ones called Reach and Impressions. (Remember, the fundamental reason to advertise is to get your business in front of a lot of people).