In this post we will discuss the different features that are available to you within your SharePoint environment. The information I am providing will be based on SharePoint 2013, but unless I specifically state the features are new to SP2013 you can assume they exist in SP 2010 as well.
Although this is the free and most basic version of SharePoint you actually get some great features from BCS. Many environments are more than capable of fully utilizing everything they could possibly need with just the foundation version of SharePoint.
External Content Types
The External Content type is the heart of BCS. 99.9% of everything you do with BCS starts with an External Content Type (ECT). ECTs basically act as the connection between SharePoint and the external data. An ECT maps all the data within the external source that you want to bring into SharePoint. I say that you want because even if you hit a data source with 25+ columns and you want 3, then you only have to bring in 3. The ECT then maps all the connections, and configuration of the data from the external data source to objects within SharePoint. The ECT in the end is really just a content type which contains columns that just happen to get their data from a source outside of your SharePoint farm.