From Online Manual
Topics (often called threads) are collections of messages grouped together under a common title, intended to reflect a single topic of discussion. Topics may have [[poll]s and/or calendar events attached to them.
Topics can have the following states:
- Sticky: This state indicates that a topic contains important information, or information that may be useful to the subject of the board.
- Locked: This state locks the topic down so only privileged people can reply to it. Common uses for this state are indicating that a discussion is unwanted, or that a conclusion has been made out of a discussion.
The default cap of topics in SMF is 16,777,216 topics.