With one Campaign, you can have multiple Ad Sets. And within each Ad Set, you can have multiple Ads.
At the Campaign level, we can see the Delivery status, overall Budget, Results, Reach, Impressions, Cost Per Result and Amount Spent.
While on the Ad Set level, the results are broken down per audience. This can be in the form of location based or customer audience based. There are also no limitations to how many Ad Sets you can have.
And when you select on one of your Ad Sets, it then takes you to the Ad level. Here you can see which Ads are performing best for each audience and make changes based on your findings. It is recommended to have more than one Ad within each Ad Set.