"this" keyword in C#

Let me try and explain this "qualify" piece.

Lets say you have the same variable name in two places one at class and one at constructor / method level.
Using the example in the article itself -

public class Employee
{
private string name = string.empty;
private string alias = string.empty;

 public Employee(string name, string alias)

    // Use this to qualify the fields, name and alias:
    this.name = name;
    this.alias = alias;
 }
}

There are two scoped name and alias variables - one at class and another at constructor level.
When we say this, we qualify the variable to be the class level one.

this.name = name;

The value of the class level variable has been set to the value passed in the scope of the constructor.