Orchestrator vs. Biztalk

Question

I had a question come up that i couldn't answer entirely because I don't know enough about Biztalk.  What are the key differences between System Center Orchestrator and Microsoft Biztalk? Where would you use one versus another? 

Answer 1

Maybe a good description of Biztalk Serv e is here
http://en.wikipedia.org/wiki/Microsoft_BizTalk_Server:
In a common scenario, BizTalk enables companies to integrate and manage automated business
processes by exchanging business documents such as purchase orders and invoices between disparate applications, within or across organizational boundaries. Human-centric processes cannot be implemented directly with BizTalk Server and need
additional applications like Microsoft SharePoint server.
Development for BizTalk Server is done through Microsoft Visual Studio. A developer can create transformation maps transforming one message type to another (for example an XML file can be transformed to SAP IDocs, etc.).
Messages inside BizTalk are implemented through the XML documents and defined with the XML schemas in XSD standard. Maps are implemented with the XSLT standard. Orchestrations are implemented with the WS-BPEL compatible process language xLANG. Schemas,
maps, pipelines and orchestrations are created visually using graphical tools within Microsoft Visual Studio. The additional functionality can be delivered by .NET assemblies that can be called from existing modules--including, for instance, orchestrations,
maps, or pipelines.
I marked the differences I see to Orchestrator in bold.
For me it looks like BizTalk is usable to exchange business documents through to different applications.
Orchestrator for me is to integrate business processes from different applications.