Create External Content Types using SharePoint Designer 2010

External Content Types section within SharePoint Designer lets us define connections to Line of Business data that we have access to as a developer, designer or admin of that site. Once the connection is defined, business analysts can use that connection to create what’s called External Lists which shows the content of what the connection is attached to (for example a table in a database).
Create External Content Types using SharePoint Designer 2010 | SharePoint-Videos.com