@computed and @tracked in Ember.js

Currently, I am working on Octanify Components in Ember.js. I can't figure out the difference between using @computed and @tracked. It's similar, but sometimes I found a problem.

@computed
get departments() {
  return this.store.query('department', { per_page: 1 });
}

In this case, removing @computed puts you in an infinity cycle. What's the problem?