thisの使い方を教えてくださいませ。

class Company
{
public void addEmployee(Employee e)
{
System.out.println(e.aName + "さんが入社しました");
}
}
public class Employee
{
private Employee afo;
public String aName;
public Employee(String name, Company c)
{
this.aName = name;

// ココのthis
c.addEmployee(this);
// c.addEmployee(afo); なぜafoだとだめなのか？
}
public static void main(String[] args)
{
Company aCompany = new Company();
Employee aEmployee = new Employee("山田", aCompany);
}
}