Explanation/Reference:
Power Pivot for SharePoint is a middle-tier data engine that loads, queries, and refreshes data models hosted in SharePoint. It is used to implement Power Pivot and Excel data models in SharePoint.
Power View is an interactive data exploration, visualization, and presentation experience that encourages intuitive ad-hoc reporting. Power View is a feature of Microsoft Excel 2013, and of Microsoft SharePoint Server 2010 and 2013 as part of the SQL Server 2012 Service Pack 1 Reporting Services Add-in for Microsoft SharePoint Server Enterprise Edition.
References: https://support.office.com/en-us/article/Power-View-Explore-visualize-and-present-your-data-
98268d31-97e2-42aa-a52b-a68cf460472e