Keep lists of people here
A list is a few people read together: what they publish — and what they believe, in their own words — in one chronological feed, as its own tab on your home page. Public by default, so anyone can read it too; private if you say so. No ranking, no notifications, no email.
Sign-in is with Google. ppll keeps your email address, your name as Google gives it, your follows and your lists — nothing else — and you can delete all of it in one tap from Settings. What is stored, exactly.