in some threads here in victory battles they are closed.why they are closed and a moderator closed them?

A thread gets closed for mainly two reasons.

1) It's too old to hold conversation.

2) The owner of the thread asked for it to be closed.

You will have the random thread that will be forced closed due to questionable content or purpose, such as SPAM or insult(s) to other member(s). And, yes, a moderator probably closed it.

Either what Jason said, or because (if it's a question thread) the problem's been solved. Just like this one, in which the question's been answered so it no longer has a use. *click*