Adjust is an app analytics platform. They advertise their product for example with how this company used it:

Find out how ABA English did it

By syncing comprehensive in-app and campaign data to their own business intelligence system, ABA English have created in-depth user behaviour models which have enabled them to see exponential growth. In three short years they’ve acquired over 12 million users, with the majority of them using their apps.

Discover how they….

Tracked all in-app events and synced all data back to their own BI platform to tie together the entire user journey

It is used in popular software like Avira Antivirus or G-DATA Internet Security Light, rendering them Tracking Software or Spyware.