Over the last couple years Microsoft, IBM and others have been working together to create a number of Web services specifications that add higher layer functionality to the popular base functionality of XML, SOAP, WSDL and UDDI. A plethora of specifications have been published/refreshed/re-written/replaced that it has been hard to get a grasp of it.
We have gone through a lot of effort at the MSDN Web Services Developer Center to make understanding the Web services architecture being built on the specifications a lot easier to follow. Below is the picture we use to categorize the different parts of the architecture that the specifications envelop.
I encourage you to check our our specifications page at http://msdn.microsoft.com/webservices/understanding/specs/default.aspx and click on the areas on the image to drill into more information. I would also encourage you to read Secure, Reliable, Transacted Web Services: Architecture and Composition for an overview of how the specs fit together and information on their specific purposes.