Activating apps vs. synchronising devices

This may seem like a very stupid question, but I have not found an answer to it yet: if I use NC to synchronize calenders, tasks and contacts on different remote devices, do I need to activate the corresponding apps in NC as well?

In other words: the apps “calender”, “tasks” and “contacts”, are they necessary to synchronize several Android devices, or are they just needed if I wanted to use NC via web based UI?