Full form for some of the .Net terms
API: application programming interface
asmx: Active Server Methods. It is a Webservice extension.
ascx: Active Server Controls. It is a User control Extension.
ASPX: Active server pages.
BCL: Base Class Library
CLR: Common Language Runtime
DLL: dynamic-link library
WSDL: Web Service Description Language. IT describes the webservice.
HTML: HyperText Markup language.
SOAP: Simple Object Access Protocol. It is language neutral. HTML + XML is soap.
XML: Extensible markup language.