Microsoft Business Connectivity Services (BCS) (formerly named the Business Data Catalog) provides the capability to allow data sources outside of SharePoint to be surfaced and potentially modifiable in SharePoint's List user interface. Use this tag for questions or problems related to configuration or using BCS.
Microsoft Business Connectivity Services (BCS) (formerly named the Business Data Catalog) provides read/write access to external data from line-of-business (LOB) systems, Web services, databases, and other external systems within Microsoft SharePoint 2010/2013 and Microsoft Office 2010/2013 applications. Both SharePoint 2010/2013 and Office 2010/2013 applications have product features that can use external data directly, both online and offline. Developers can gain access to a rich set of features and rapidly build solutions using familiar tools such as Microsoft Visual Studio 2010/2013 and Microsoft SharePoint Designer 2010/2013. MSDN.