Each campaign created with McAudience and the Enkronos Apps engagement applications you continue to build up your Users Pool (Read more about Users Pools in Data Gathering -> Users Pool). By doing more and more campaigns, you will continue to expand your information regarding your users and as such each next segmentation of users will be more precise.
The difference between Facebook and Google Ads and McAudience is that while in the paid add campaigns of those platforms, you lose the users that were only reached. On the other side, in McAudience every user that interacted with the Enkronos Apps on those add campaigns will stay in your Enkronos Apps user pool. Which makes re-targeting of exactly the same users simpler.
Read here about the next feature Billing.