OPC - OLE (Object Linking and Embedding) for Process Control :: The Industrial Interoperability Standard
Automation, Control & Plant Intelligence - Articles, Analysis, Reviews, Interviews & Views
VSTO = Visual Studio Tools for Office
A generation of Industrial Software Programmers/Systems Integrators and End Users has been using VBA to develop applications. Now Miscrosoft is trying to push a new technology - VSTO
VISTO is an alternative to VBA, and will most likey will replace with VBA in time.
It looks like Microsoft is going to discountinue VBA in its new releases from 2008 on. At some point you may have to move to it while upgrading your existing systems.