there are two separate sections, as named above. Can someone please tell me what is the difference ... ?
Watches for sale is for dealers, the private watch sales is for people who occasionally sell something.
Watches for sale are from professional watch dealers whilst private sales are, as said, from private sellers
Also, as you may notice, the threads from the Watches for Sale section do not show up in the "Latest" tab (to prevent cluttering the forum I suppose), whereas Private Watch Sale threads do.
While that's somewhat true it's not always. As stated from one of the mods via PM if you have multiple watches for sale concurrently the "Watches For Sale" subforum is the preferred posting area. For a single item at a time the "Private Sales" subforum is preferred. Basically the mod didn't think it was appropriate to have multiple listings pushing down others from the first page if the other sellers were just putting a single item up for offer. There are more than a few private sellers and collectors who post in the "Watches For Sale" subforum as their inventory warrants it.
Yeah, it mainly has to do with how often you sell watches, not with your status as a "professional dealer". If you are very frequently posting sales threads then your posts belong in the Watches for Sale section.