The topic is the subject one brings about for discussion. A thread is the collection of messages ensued by the topic, consisting of the original post and potential replies--in other words, a conversation between users.
Topic: Wario's vulnerability to cinnamon rolls.
"How many cinnamon rolls does it take to give Wario a heart attack?" (Original Post)
*"5, but it heavily depends on factors like the pastry's consistency and how much sweets Wario can canonically ingest"
*"i have a bad feeling about this thread"
*"his stomach is like a black hole, so infinity"
*sarcastic mod comment as they prepare to lock and move the thread to Topic Storage