White Label is when you offer website building services, create websites for your clients (design, implementation, consulting, etc) and when your clients login into the app they see your branding instead of Brizy.
In this case the billing for your services is done by you, outside the system.
Reseller is when you (re)sell the Brizy platform as a whole, you give the Free plan, you offer a PRO plan, on your website. We manage and handle all the payments from your clients via the reseller program. You receive the cash each month at the end. You only need your website where to promote and sell your Brizy Cloud platform.
In this case the billing for the platform is done by us for your clients, and the platform is fully white label, that means your clients will buy access to your branded cloud website creation platform.