The chapter in the very beginning that explains .NET was very hard on me indeed.If someone would be grateful enough to explain meaning of .NET in simple words, I will appreciate.

the simplest explanation would be .net is development frame work and a runtime where .net code executes. It would be similar to Java sdks and runtime of the Java world.

.net languages get compiled compiled into the MSIL (micro soft intermediate language) the MSIL is then executed in the CLR ( common language runtime ).

Similar to Java in that Java is compiled into Java byte code and then is executes in the Java runtime.