One can easily get lost in the alphabet soup that is datalink.

Both ACARS and ADS-B provide datalink applications – which can be broken down in terms of CNS: **C**ommunication, **N**avigation, and **S**urveillance.

* ACARS is used for:
 * Communication: includes uplinking (ground → aircraft) **weather** data upon a downlink request to the company/service provider – not a public service
 * Navigation: if you consider flex-routing
 * Surveillance: position reports in the North Atlantic for example.

* ADS-B is used solely for Surveillance; broadcasting (OUT) own location – and can include ownship surveillance by receiving (IN) traffic information.
 * If this IN setup is via the UAT frequency, then the aircraft can also receive **weather** information using [FIS-B][1] (free service). Its only relation to ADS-B *in this particular instance* is the UAT frequency, and it is more of a general aviation (and low-flying commercial) service.

[![enter image description here][2]][2]  
Source: https://www.faa.gov/nextgen/programs/adsb/pilot/#fisb


  [1]: https://www.faa.gov/nextgen/programs/adsb/pilot/#fisb
  [2]: https://i.sstatic.net/ksZGX.png