As a Seller, you can create an unlimited number of listings and deals. You can create listings without deals, but can't make deals without listings. What's the difference between these two?
Listings
When you "Create New Product/Service", you're making a listing. This is where you'll tell us, generally, what your company offers - not which specific deals/discounts you're advertising.
The listing is where you set the target audience.
You must add a marketplace as a target audience in order to select that marketplace in specific deal segmentation.
Changes to listings will apply to all deals within that listing, so exercise caution when making updates or publishing/unpublishing. If your listing is unpublished, so are the deals inside of it.
Deals
When you "Create New Deal", this is what Buyers see when browsing marketplaces. Deals are where you'll add details about the specific deal/discount you want to advertise, designate who can use it (this is called deal segmentation), and provide instructions on how to get it.
Every deal can have different details and segmentation. You're not limited based on what listing each deal is in, so create deals based on whatever works best for your organization.