What did Aristotle mean when he said ethics was a practical rather than a theoretical discipline?
As to the first part of your question, ethics are practical because it provides us with guidelines of behavior that result in a stable and potentially thriving community and society. By having a measure of behavior and consequence, we can promote those actions that most benefit the individual and, most importantly, society. It just makes sense to teach everyone to act according to a plan that will benefit all. Practical.
