B2B Key Performance Indicators (KPIs) are metrics tied to specific business goals, such as quarterly sales. While there is a great deal of crossover between B2B eCommerce KPIs and general eCommerce metrics (e.g., you may have a KPI for increasing conversion rates within a given segment), the two concepts are distinct.
Metrics, in and of themselves, are not tied to specific goals. They simply point to the raw data that will inform your strategy in a variety of ways. Your metrics may be mentioned in your KPIs, but they are not KPIs themselves.