ASP.NET Web Services is basically a tool from Microsoft, which could be used to create and build web pages, and web technologies. ASP in ASP.NET stands for Active Server Pages. These tools help programmers and developers to build dynamic, rich websites, and web applications using compiled languages like C#, VB, etc.
If you wish to learn dot NET and want to get certified in it, check out the .NET course from Intellipaat. And also, look at the following YouTube video on Dot Net Full Course.