Excel Services is a business intelligence tool that allows you to share data-connected workbooks across an organization.
Excel Services in SharePoint Server 2013 is a shared service that you can use to publish Excel 2013 workbooks on SharePoint Server. The published workbooks can be managed and secured according to your organizational needs and shared among SharePoint Server 2013 users, who can render the workbooks in a browser. Excel Services was introduced in Office SharePoint Server 2007 and is available only in the Enterprise edition of SharePoint Server 2013.