What does "responsible" mean when you're talking about animals?

Animals are a huge part of our lives. Even if we don't own an animal, we likely use animal products every day. Everyone says you should use animals "responsibly." What does that really mean?

Being a responsible owner

Responsible breeders - is there such a thing? And do responsible breeders sell on the internet?

What is a "puppy mill?"

Farming - are they responsible or are they in it for the money (factory farms)?