Hmmmm.... Ok, lets do them all:
A post is a single entry by one user at a time. When you create the first post of a new topic, you create a new thread simultaneously. A the number of posts increases, so the thread will gain length and form extra pages.
A thread is one or more posts that cover (usually) a single topic.
When you entered your text above and either clicked
post quick reply, or
submit, (depending on which editor version you used) you actually carried out a submit operation, which created the thread. ok?
You did in fact submit to the wrong forum BTW. I believe chit-chat, or testing is appropriate.
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