AuthorSend gives you three tools for organizing readers. They overlap a little, so here's when to reach for each. All three live under Subscribers.
Lists
A list is a group a reader belongs to — "Newsletter," "Launch team," "Free magnet." A reader can be on several lists at once. Lists are usually where a signup form adds people.
A list only ever mails people who are actually subscribed to it. When someone unsubscribes, they stop counting and stop receiving that list's mail automatically — you never have to prune it by hand.
Tags
A tag is a label you attach to a reader — "bought Book 1," "clicked launch email," "VIP." Tags don't group people into an audience the way lists do; they record something you know about a reader so you can find them later. Tags are often applied automatically by a journey.
Segments
A segment is a live filter, not a fixed group. Define a rule — joined in the last 30 days AND opened the last email — and the segment always reflects whoever matches right now. You can nest AND/OR conditions across dozens of reader attributes and behaviors.
The Blocked list
Under Subscribers → Blocked is your suppression list — addresses you can never email again, such as people who marked you as spam or hard-bounced. AuthorSend keeps this list for you and honors it on every send. See Manage unsubscribes and blocked addresses.