If you are already using the TraceTogether App i.e. keeping the App open in the background and keeping Bluetooth on, you do not need the TraceTogether Token :) You only need either one of them, to get notified quickly if you've been a close contact of a COVID-19 case.
Similarities and differences between the App and the Token
Both the App and the Token use privacy-preserving Bluetooth exchanges, to record encounters with other TraceTogether devices around it. Such proximity records help contact tracers establish close contacts more quickly and comprehensively.
Given that the App has a user interface, it's able to support additional features such as letting users see their Vaccination/PET Status, SafeEntry history, and possibly more features in future.
Then why is there a need for Tokens?
While some prefer the convenience of having the App on their phone, there are others who do not have a compatible phone. The Token allows us to extend coverage to more people.