The Business Data Catalog (also known as BDC) existed in Microsoft Office SharePoint Server 2007 (MOSS, not Windows SharePoint Services). It’s gone.
Business Data Connectivity (also acronym’ed BDC, though it’s now Connectivity, and it plays a very similar role) was introduced in SharePoint Foundation 2010 (also SharePoint Server 2010, of course). This BDC’s job is to provide connectivity to back-end data systems, as was the job of the BDC (Catalog) in MOSS 2007.