What is meant by XML/XSLT/XPath and asynchronous programming?

Question

I understand that (1) XML/XSLT/XPath and (2) asynchronous programming may not be related to one another. My questions are:

1. When a C# developer job is advertised saying: "the following skill is required as mentioned in 1 and 2", what does it actually mean?

2. Lets say I need to master these two topics (1 and 2). What do I need to do to accomplish that skill? Are there books for intermediates that actually teach that info with practical scenarios and case studies?

Answers are much appreciated.

I have worked XML packet crafting for message exchange over the network, developed some amateur XML parsers for some projects and done message exchange for a client/server-based messaging system using asynchronous calls. But I really need to know and learn what the companies are looking for when they write these things (1 and 2) as requirements in their job advertisment.

Aggregate skills required for the specific job were:

• ASP.NET 2.0 (OK)
• Web Services and .Net Remoting (OK)
• XML/XSLT/XPath (?)
• Asynchoronous Programming (?)
• Windows Services (OK)
• Javascript/XML/AJAX (OK)
• Microsoft Silverlight/WPF (OK)

So firstly, it's clear that AJAX is not related to Asynchronous programming (in this very specific context) as it is written as a separate required skill (and I hope that it's not a mere redundancy). In normal cases, my deductions would have been the same like asynchronous programming means working with AJAX (asynchronous JavaScript with XML).

Secondly, making a web service in C# does not require any extensive experience with XSLT. In fact, exposing functions from a DLL (encapsulating business logic) is the simplest of any task with web services in C#. I wonder if there is some extra skill or experience that is needed?