There are two product sources for TikTok Shop Ads: TikTok Shop and Showcase.
TikTok Shop: Products that have been uploaded to TikTok Seller Center. You can connect TikTok Shop to your Ad Account for advertising purposes in two ways:
Showcase: Products that are currently displayed on the TikTok Account. You can access Showcase by connecting your TikTok Account to your Ad account for advertising purposes.
Learn more about TikTok Shop and Showcase.