Hello, Biztalk Services was the old name of .NET Services. But after a year's evolving, .NET Services is now very different from what Biztalk Services was.
.NET Services is also different from Biztalk Server. The former is a cloud service, while the later is an on-premise server. Actually we can say they're completely different, that's also one reason why we no longer call it Biztalk Services.
I suggest you to begin with the introduction on
http://www.microsoft.com/windowsazure/dotnetservices/.
Lante, shanaolanxing This posting is provided "AS IS" with no warranties, and confers no rights.