First of all you do not do anything in your Main method which is the entry point of your programme.
You defined a class named Greeter but you never us it.
A class ist nothing but a prototype for an object.
In order to see "Hello object world" on your screen
you must
1) Create an instance aka object of your class like this
var myGreeter = new Greeter();
2) Then you must call the Greet method like this:
myGreeter.Greet();
Moreover I would like to recommend you this tutorial:
http://www.charlespetzold.com/dotnet/DotNetBookZero11.pdf[
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